Sure there's some upfront email blockage/filtering that goes on, but that's essentially other UI tweaks in camouflage.
I'm not saying UI isn't cool! For sure some of the things they talk about sound interesting (like the reply later stacks at the bottom).
For the general tech-savvy people all the UI you generally need lives behind a highly functional "search box": "give me all the email i read yesterday in the evening"; "reply to emails I tagged with 'important' last week"; etc.
Overall I think they're trying to solve problems that are encountered by so called "famous email addresses" (the founders most certainly fall in this category) where your email has been sold to a bunch of lists over and over so you really need a kind of "block this forever" kind of functionality. But how famous are most email addresses?
In general, sure, a cool, sleek new looking UI for email, I like it!