I get a very strong 1960s Bauhaus graphic design feeling from this. That makes it feel like yet another fad.
You could argue "but this is well researched so it cannot be a fad" but I think they're focusing on the wrong things. Sure, the send button is 4× faster to find according to their research – but I don't want a huge send button near the keyboard. The send button is the most dangerous button in my email client! I'd like it to be small and require deliberate effort to hit.
(Besides, it doesn't move around – I hope – so I will already know where it is when I compose my email. I'm not shooting down a fighter jet. I don't need to acquire the target quickly.)
On the other hand, this seems to be Google backtracking and saying "Ooops, sorry, our previous recommendation of a UI where all components blend into each other looks sleek but is hard to use" so I guess that's an improvement.
honestly, i don't see bauhaus here. at least not at first glance. on the one hand, i'd say it's trying to go in the opposite direction, with this "expressive design" idea, whatever that means. it immediately makes me think of maximalism (which is the opposite of bauhaus). on the other hand, you can argue that there's more of an "artistic" take to this type of ui design.