It's complicated. Chrome won't block 3rd party cookies by default. But it will present the users with a choice of whether to block them (with what exactly that means TBD). If most or all users choose to block them then it would have roughly the same effect as blocking third party cookies by default would.

Though regardless of that, Related web sites (or whatever that set is currently called) does present a hole in that logic. It was originally meant to allow sites with different domains to share cookies/storage (like google.com and google.co.uk). From what it sounds like, bad actors are using it in the expected ways. There were supposed to be mechanisms to prevent this, but it seems like they failed in this case.

The list is in a public repository however, so Brave could have filled issues and a pull request to address the issue. Instead they decided to stage a meaningless survey and declare Chrome a threat to people everywhere.