A. Does anyone actually use iOS on Mac?

B. This is actually platform consistency for iOS developers. If you are building an iOS app, you should be fairly comfortable knowing it will be running on a locked-down device, particularly if it’s a social media app with anti-robot technologies. You shouldn’t need to engineer around macOS blowing a hole in that security. If you could run iOS apps on macOS without SIP, what is iOS security good for again?

B is clearly anti-consumer. Software running on “my” hardware should be in my control.