I see everybody freaking out about unfettered payment access to one's bank accounts and I keep wondering why people don't jump to the obvious solution of simply only giving it a single purpose or limited fund credit card number from privacy.com or something.

Am I missing something with the concern about ability to constrain the blast radius?

I would call that kind of thing "a very structured framework and guardrails". You'd have to come up with entirely different solutions if you want the agent to receive payments or monitor your budget.