Charitable explanation: by allowing people to use WhatsApp/signal etc without holding onto the sim card, it opens them up to risk that someone else gains control of the phone number, and can then take over that account.
But that doesnt really require that the number stays in the same phone, just under the same persons control. Periodic SMS code check-in would be sufficient.
This is definitely a shower thought. Good news, at 24 there is plenty of time to backtrack and reroute.
I'm a bit similar, I am only in my current career because I responded to an job ad email that was later rescinded.