In addition to the simple whitelist behavior, on the initial Hey screening you can (with a single click) route second-tier messages into Feed and Paper Trail, which is a much better UX than what you can build in gmail by creating a filter for every sender that labels + autoarchives.
If that's HEY's value proposition, then they're in for a rude awakening. Personally, I think the proposition is simply using something other than Gmail, which is a fine enough reason without needing to put any marketing spin on it. $99 for an alternative though is a difficult ask.
If you think this is just "marketing spin", I think you're simply not part of the target demographic, which is people that have currently have issues with e-mail.
There are a lot of features I like, but I don't really get all the fuss about the screener. You're still getting those emails, they're not getting in your "imbox" but you still have to review them.
In practice it doesn't seem to make a big difference with gmail "mark as spam".
Sure, but the point is that you can do this only occasionally (e.g. once a day), whereas with gmail they take up space and attention in your inbox until you get to them.