That is not, thankfully, how that works ... There are, indeed, non-mobile numbers and they are second class citizens with regard to shortcodes and SMS 2FA, etc

That is not, thankfully, how that works ... There are, indeed, non-mobile numbers and they are second class citizens with regard to shortcodes and SMS 2FA, etc. You will have difficulties, for instance, if you try to adopt a Twilio number (or similar) as your primary phone number. But it has nothing to do with identification, per se - the most anonymous, cash-bought, found on the street SIM card is a real mobile number and will work perfectly ... ... and the most fully ID checked, personally identifiable VOIP number will work very poorly with 2FA (and not work at all with shortcodes). I am not sure about your specific anecdote - what carrier are you using and is your "number" the number on your physical SIM card ?