This is a modem, it itself is the client of a cell tower/base station. So unless you put it in a faraday cage with the base station next to it, 2G is almost certainly enough.

The better reason to put a 10G transceiver in this would be that some (cheap, honestly garbage) SFP+ transceivers can’t negotiate anything between 1G and 10G. But I’ve only seen that on bargain-bin hardware so I don’t know that they should be designing products around it.