-1
I’m not entirely sure, but I think the reason players cannot move or perform other actions while in queue is to avoid conflicts with in-game events.
For example, if you are walking through grass while in matchmaking queue, you could trigger a wild encounter and then immediately get matched for a PvP battle. What should happen in that case?
You might say the encounter could simply count as running away, but what if that encounter was a rare shiny Pokémon? Then players would understandably complain that they lost a valuable encounter because of the matchmaking system and ask for reimbursement or compensation. That would create unnecessary issues for both players and staff.
So while the suggestion sounds convenient, it could lead to many complications.
Also, while waiting in queue, you can already access the PC. Beyond that, I’m not sure what additional activities would be necessary during matchmaking.