That's the funny thing about Siri. It has since Day 1 insisted on being exclusively online-only, processing on the server - even for commands that the pre-Siri Voice Control could do fully locally on an iPhone 3Gs such as "Call Steve" or "Turn Wi-Fi on"
That decision always surprised me, and it's surprising that Siri's never improved given that unlike Apple Intelligence it is not limited to on-device nor to PCC.
For all the scorn directed lately at the "Apple Intelligence" team for not shipping anything they promised, I have to hand it to JG's team for at least building a local processing capability plus having PCC instead of just one server-side thing and a "Trust Me Bro" like Siri.
If we're lucky, they'll build new Siri stuff from scratch using local + PCC, and finally push the old Siri stuff into the scrapyard where it belongs.