My guess is that non beta phone is a carrier branded phone, while the one you initially tested was an unlocked variant which tmobile has not released the update to yet.
The beta is tied into your Samsung account, so the moment you put another Sim inside of your phone it won't recognize the new number as associated with your members account. the non-beta phone you put the SIM card into might have been a carrier branded phone with U software as opposed to U1 software. an alternative route is to use Odin and flash carrier version software onto your phone which will update you to Android 11
Please follow all community guidelines before posting