In Screen Time -> Content and Privacy, there's a setting to switch Siri to 'Siri Classic' which strips out the Apple Intelligence-backed behavior specifically.
Instead of "Siri Classic", I selected the "Don’t Allow Siri" option, but it didn't help. The "Siri" (Siri AI.app) process keeps running regardless.
Instead of "Siri Classic", I selected the "Don’t Allow Siri" option, but it didn't help. The "Siri" (Siri AI.app) process keeps running regardless.