Has anyone gotten their insider code denied cuz of overused code?

Title. Basically got a code from a reddit post, but realized multiple people have been able to use it before. It got through, I got a tracking number and everything, but insider website shows the status as submitted (not yet approved or whatever). It maybe a glitch or something that the system somehow let people through on duplicate code?

Anyway, I am kinda afraid to switch all 3 of my lines over to Magenta Max and get new phones cuz what if this doesn't work?? If I get denied, then I would be forced to stay at t mobile and pay the original price every month. I was wondering how often this sort of stuff happens or if it has happened to anyone at all.