Huh? I ask Siri to look at images all the time - and you're overlooking the part where I said "when you explicitly direct it to", as in by default there is no screenshot and it's never required for anything.

For example, on Mac, Command+Shift+5 will send the selected region to Siri once you enter a prompt to go with it. On iOS, after taking a screenshot, you can share it with Siri by tapping the "Ask" button. Neither of these are automatic or required, they're just alternative ways to use Siri.

Also none of these are sending the screenshot "to Apple" as you describe. PCC runs partially on Apple infrastructure, but provably (not a typo of "probably") does not allow Apple to see or review the actual queries or their responses.