Your comment still doesn't make any sense. Either you want the highest verification tier and go with phone verification, or you don't. It's your choice as admin. As a user you can just delete the phone number from one account and use it to verify another... you will have a timeout [2] but both accounts will be verified. Is it annoying? Yes. Is it understandable to rate limit it? Yes. Is it impractical? No.
I can't remember why but I had to switch my phone number from my personal discord to my work discord, either to get it to allow me to login from my iOS Discord or something else asinine. I remember it took me maybe 40 minutes to get into the thing, haven't seen anything like it.
They're weird about it, sometimes you have to and sometimes they never ask. It's not like Twitter where you can use the site for an hour before they force you to verify. They probably do it so people will say what you said when people point out the problems with it.