I've set up Wireguard on a Linux laptop running Ubuntu 22.04. I've tethered it through my phone's mobile data service, and then started the Wireguard connection on the laptop. That seems to be working fine — I can access the pfSense web admin page; I can download large test files from my test device; I can upload large files via SSH.
So, that indicates the problem is really with the Android Wireguard app, while the pfSense Wireguard implementation is fine.