"Do all routers these days "phone home" anyway and modify settings on autopilot?"

Depends.

"Homemade" routers running open source OS that computer owner can compile themselves need not "phone home" against owner intent. "Home" is the computer owner, not some company.

Commercial routers running closed source OS that owner cannot edit and re-compile can be expected to try to phone home for something, IMHO. A disturbing trend certainly not started by ASUS but which seems to be infecting most hardware sold with pre-installed closed source OS.