It's a FromSoft game with souls mechanics. I wouldn't call it a souls-like personally, but it's more of a souls-like than some other games I've seen use that genre name.
I wouldn't say the combat is an important part of the genre though honestly, even though it is one of the most recognizable parts of the games. I'd say the largest pillar is exploration, usually in a world that doesn't feel like it's designed for you. Another big one is, usually, that death isn't a failure. You don't reset and lose progress. Death, in itself, still is progress (but you usually need to collect your currency).
People will usually talk about the combat (which has changed a lot in the genre, so it isn't that important), or the difficulty (honestly, Elden Ring in particular is pretty easy, so I would say it obviously isn't critical). It's all the little things that really create the genre though. I could easily see a walking sim through a mysterious castle being a souls-like with no combat and only puzzles.
Sorry for the rant. Lol. I forgot what this was about for a minute. All of this is to say I could see AC6 being a souls-like, but I don't think it fits perfectly. I wouldn't argue with someone including it though.