I'm not going to keep posting the same thing for a while on this thread but I hope Oda does not trying to downplay Sanji again. He had ALL THREE of Luffy, Zoro and Sanji learn Haki in the timeskip. And they were the only three who did. So far Luffy and Zoro have unlocked Conqueror's Haki, Luffy did so before timeskip and because Rayleigh it seems it was presumed Zoro would. Zoro got his after timeskip.
Again, the Zeff who hinted Sanji was like Luffy and Zoro but it is hidden.
Now the other thing they showed training flashbacks from both Luffy and Zoro getting direct training.
It would be ridiculous if Sanji being trained by a founding member of the Revolutionaries, that was on God Valley (even if just a kid) and shown able to handle fighting Kuma who was just shown, while damaged, being able to survive Akainu and able to harm Saturn, did not give Sanji adequate training for the New World. The other two you presume have CoC (Mihawk and Rayleigh) but again, it is stated it can't be trained so Ivankov not having it doesn't necessarily mean a thing, although possibly has traits a bit and is a ruler of a land.
Ivankov was shown durable enough to survive both Magellan and Akainu. He did not even fight Akainu seriously (not saying he'd win), and Sabo was shown to be able to hold his own against an Admiral. I would hope Oda was just hiding how strong Ivankov was and we are left to assume based on her exchange with Kuma and then Kuma vs Saturn.
I doubt the revolutionaries, including Ivankov were included in Doflamingo's throne Wars and they are weak. And Ivankov has special techniques like the recipe stuff he made Sanji go after. So my guess is Sanji learned, not specifically that but ways he could make his own versions of the techniques.
I would presume, that Sanji is eventually going to get an Ifrit Jambe version of Hell's Memories but the whole being trained by a Commander of the Revolutionary Army and not having strong CoA and CoO seems ridiculous. Ivankov had planned how he was going to break out of Impel Down and everything.
I would hope given the current situation:
The matter of Ivankov being on God Valley, the Celestial Dragon game, the Knights appearing and that Ivankov trained Sanji like Ivankov's God Valley situation that this arc is more of Sanji one, where he gets more advanced battle development.
Especially now that we basically see Oda had Sanji go in Ifrit Jambe to do a combo attack while Zoro was in a basic form or the attack he used on Kaido that cut slightly. And Luffy wasn't even in Gear 4th. Otherwise it's kinda just messing up the whole monster trio and the fact that Oda gave only Luffy, Zoro and Sanji Haki in the timeskip.
Like I hope that is Oda's indicator that Sanji is getting ACoC too. Only those three need to have it from the pre-Yamato made a member group.
Usopp fits the character of more the wizard on the journey who is not strong but uses magic, like in those RPG games. Same with Nami, although I'm hoping for Oda to decide to enhance them somehow physically. Although technically Sanji's cooking was supposed to be the strengthening excuse.
Speaking of, given the whole Ivankov manipulating hormones and the Germa genes thing, it would be interesting if Ivankov actually did use his ability on Sanji in a non gag way, and it in combination with his German genes, basically interacted with each other to basically give Sanji some power upgrade that is not gender shifting. To me it would be explainable. As Oda already called him Ivankov of Miracles. Interesting he met Luffy in a prison where he treated Luffy for poison using hormones, and Sanji was freed by poison pink from a prison. Sanji saved by Ivankov, Luffy saved by Reiju. To save Luffy, non gender changing hormones were used. Ivankov said it required a strong will power, which then indicated Luffy is like Dragon in terms of willpower. Luffy then was shown to use Conqueror's Haki. We presume Dragon has it too. Sanji, back to the above Zeff thing, latently having strong willpower, and Ivankov's hormones at some point taking affect on him to awaken latent abilities. Ivankov's indicating it's up to Luffy's willpower is similar to the whole Rayleigh can teach Haki but CoC has to be manifested by the individual. So hopefully Oda goes that route, using the thing we presumed as a gag as a pre-situation hint that Sanji got some hormone altering later by Ivankov. Again, not like gender change stuff or the girl techniques. But something in the league of Ivankov made Luffy constant able to get up and fight again, basically something strengthing Sanji greatly.
Given the devil fruit was made a prize along with the one Kaido got which is said to be insanely powerful and helps make him invincible somewhat, there has to be maybe something Oda comes up with. It would also tie back into the closeness of Kuma and Ivankov, then Kuma and Vegapunk, and Vegapunk and Judge and Sanji being somewhat like what Kuma became (even though Franky is more like that), and that Sanji may basically be a prototype of the Pacifista and Seraphim stuff in a sense.
If you consider Luffy and Blackbeard had similar situations, defeated by Magellan then rescued one may presume Shiryu and basically Ivankov are close on level, though I'd bet Ivankov stronger, then Sanji having weak CoA is nonsense even if it is not his speciality. Oda needs to speed up Sanji fighting development.
I'm not getting my hopes up because Oda likes to make Sanji like a weakling in the monster trio instead of having him beat renown opponents. The whole cook thing is nonsense simply because why making him the number 3 and a main fighter if he is just a cook.
Hopefully Oda improves all the Sanji battle prowess soon, so we can get back to the officialized Yamato in the crew.