I don’t think it is “forced”, just the new default (unless explicitly disabled in a view), which is nice to see. Additionally, I didn’t see much relevance to Play Store - it seemed to be a system-level thing.
The security tool will work in the background to detect apps that use suspicious permissions, like the ability to spy on screen content or read SMS messages.
There was also a similar product that made your headphone jack a button. Nonetheless, I don’t really think phones need more physical buttons these days.
IIRC their point was that SMS is insecure, so they don’t want people using SMS in Signal to think that this is Signal. With RCS, they could do what Apple will - be interoperable while providing extras with own platform (iMessage).
Admittedly, that doesn’t sound like enough reason to reimplement SMS and RCS alone would still be kind of inconvenient.