Weren't Natsu and Gajeel playing the Twin Dragons from the start though? If I'm not wrong about that, the scenarios are too different.
Against Sting and Rogue they were clearly holding back since (IIRC) they comment on how they were learning their attack patterns, movements, etc.
In the case of Mira and Elfman neither made any comments alluding to anything like that, they just called them strong. Of course we have to accept that Mira did hold back due to her canonically having strong Souls. But Elfman? Even if you want to say he held back, you still have to somehow explain Elfman's Soul going from being hurt from hitting Madmole to surpassing the striking strength of an FDK Demo Fist. That is far too drastic of a difference to be explained by Elfman holding back.
Tbh I don't think it even needed justifying that much, he had a Soul that was made to counter Sand Magic and had assistance from Lisanna (which protected him from the one sand attack that would have saved Ajeel). Ajeel isn't exactly particularly strong even by Spriggan standards either.
Mira holding back is a weird part of this tbh, since it makes her look stupid as hell. "If we continued fighting, would we even have won?" - probably, if you'd just gone into a stronger Soul from the start? At least when Team Natsu lost to the DE's the first time around it was because they were shocked by their abilities and the fights ended before they could enter stronger modes (or use more suitable attacks in the case of Natsu). With Mira and Elfman, Mira just stayed in base for no reason. So while I do agree that Mira held back (in that she wasn't using stronger Souls, I think she definitely wasn't pulling punches even though she was in BSS), that only makes the entirety of the fight stranger to me since its still weird for Skullion to go from being completely undamaged by physical and Magical attacks to being scratched up.
As for Elfman though, I suppose we'll only see as time goes on whether that was his strongest Soul or not. But for now its the strongest he has, and going from being hurt from hitting a passive Madmole to scratching him up makes no sense when this is a guy who shrugged off an FDK Demo Fist. Like I said above, its too drastic of a difference to just be a case of Elfman holding back when in the exact same Soul.
My final stance on this is that you're right about Mira holding back but I don't buy Elfman holding back at all, and even though I accept Mira was holding back, its still weird as hell that Madmole/Skullion went from being completely untouched to being just as scratched up as the Strauss'.
God off-panel fights suck lmao
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Where did I claim Madmole and Skullion are immune to damage?
I was the one that raised Skullion being hit by Gray in the first place.
Not sure if you're purposefully being disingenuous here but Natsu hurting Madmole in their second battle does nothing for Elfman's case. The manga makes it clear that Natsu isn't damaging him conventionally, instead he used FDK Purgatory to surpass Madmole's heat resistance:
If anything Elfman's feats in this off-panel fight look even more suspect since god damn Natsu chose to overpower Madmole through heat rather than actual striking power. So yeah, Elfman damaging Madmole to such an extent while in the same Soul that got hurt just from hitting a passive Madmole is looking like some
major BS.
The point I've being trying to make is that Madmole's and Skullion's durability is pretty damn impressive. So when they get scratched up in an off-panel fight, an off-panel fight that they were clearly winning at the start since Mira and Elfman were damaged first while they were unscratched, something is weird when the fight ends with all parties looking equally damaged.
Just to repeat, no they aren't immune to damage but that wasn't my point and you would have known that had you bothered to read my previous reply.