> One simple example is an extension can't see cross origin iframes

Sounds like a skill issue, our web agent is able to interact with cross origin iframes to for example solve captchas: https://www.youtube.com/watch?v=LD3afouKPYc

We honestly haven't faced any bot detection or blocking issues. Owning the browser layer exposes to you much more detection just look at Comet getting blocked on Amazon etc.