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 spi

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.