I feel like we're losing the plot here. Removing the cancel capability of onBeforeRequest didn't improve security much. It did, though, hobble ad blockers to just dealing with static lists if they want to prevent an ad from downloading in the first place.
Removing the onBeforeRequest redirect didn't add much security either, since you can just ask for permission B instead of permission A and just inject code. Though, ad blockers don't need that anyway.
It only sounds insane because you're saying "want extensions to snoop" to describe "want extensions to run a function call locally".
It is a permission that could be used by a malicious extension to snoop, but that is far from the only use. Wanting the permission != wanting snooping.