> The strong sense I got from reading this is that they don't believe it's possible to safely do this sort of thing right now, and they want to warn people away ...

This is directly contradicted by one of the first sentences in the article:

  We've spent recent months connecting Claude to your 
  calendar, documents, and many other pieces of software. The 
  next logical step is letting Claude work directly in your 
  browser.

Ascribing altruism to the quoted intent is dissembling at best.