Pretty much accept nothing alike at all.
Lol really, you're going with "AC Japan"
LMAO
Other than the focus on acrobatics and stealth killing in an open-world environment, honestly I'm just basing that assumption off of how much Sony's first party games have resembled Ubisoft open-world games as of late.
Spider-Man to me felt like "Assassin's Creed except you're Spider-Man". You jump all over the place, do some melee combat, gather a shitload of collectible icons that have been spread all over a map, earn XP, spend skill points on a skill tree with three branches, collect loot which you'll use to craft shit, manage gear levels, and maybe rifle through a lore codex, all represented by tabs lining the top of the menu screen.
If Tsushima doesn't do that stuff I'll honestly be surprised. but look at Spider-Man, Days Gone, Horizon Zero Dawn, and God of War. When I played those games they felt structurally just like AC, Watch Dogs, and Far Cry. I'm also kinda basing this on the Sucker Punch's Infamous games which followed and earlier version of that formula.
Basically I'm saying Tsushima looks like it's gonna be another AAA open-world game. Maybe my guess is totally off and it will be closer to a Naughty Dog game or something, but that's not the feeling I get when I see the horse and the open world, and judging by the developer's past work.