I don't think you know how the TOC placements are decided. At the end of every issue of Jump, people are allowed to vote for their favorite series of that week, and those results are then used as a reference for creating the TOC.
If it was based on sales alone, then the TOC would be the exact same every week, but that obviously isn't the case. It's more based on popularity among those who read the magazine, regardless of whether or not they plan to buy the volumes. Phantom Seer most likely is popular among people who don't read Jump or who simply don't vote for it, which is why it does not place highly in the TOC.
We have instances of series placing worse than you might expect, but very, very few of a series placing higher than it deserves. Gag manga generally sell worse than battle shounen, but it isn't hard to believe Magu-chan is more popular among people voting week-to-week than, say Cop & Dolphin, (or that HSF's chapter from 8 weeks ago happened to be very well received). There is a very stark difference between Mitama ranking above Yozakura, and Elusive Samurai ranking above both Dr Stone and Black Clover.
So because Elusive Samurai came second in the TOC, we can assume with pretty high confidence that was received very (if not extremely) well. This does not mean that it will sell as well as AssClass, of course, but to say that we can't trust the TOC in a situation like this is kind of ridiculous. There isn't a reason for Jump to lie about Elusive Samurai in the TOC when they didn't for any other veteran authors (including Kishimoto, and he had a massive campaign leading up to Samurai 8).
But there's no reason to discuss this any further until we see future TOCs, since Elusive Samurai could obviously drop hard in the following weeks and this whole discussion would be pointless.
