When you compare Signal with Telegram on this axis you actually end up with Telegram being "safer". Because while Telegram needs phone number for initial registration you can just throw the SIM away after that (how to get anonnymous SIM capable of receiving SMS is left as an excercise for the reader, but I believe that getting reasonably anonymous burner SIM for this single use is possible and even easy anywhere in the world, with the extreme approach being "borrowing" it from some random IoT device) as the authorization of new devices occurs in-band.