[pwg]

It is how the old copper PSTN network worked, and if you are lucky enough to still have an actual copper PSTN phone line it is still true.

[Rjevski]

My argument was that even if you did have an “actual” copper line it would eventually be terminated at a device that speaks analog phone line on one end and spits out SIP on the other end.

This specific hanging-up behaviour was an artifact of older analog switches and I didn’t think they would emulate it in the software-based SIP switches but according to the comment above it’s still the case.