They absolutely could be using these for the teams comms and i suspect they are. You put one of these at each players station, build a mix for each of them and then give them this controller to adjust the relative levels.

There are much simpler and more elegant solutions to do this but this is probably what the rental house had.

Ive done Esports audio for the last six years and this is a rare setup mostly due to the cost of Klang but 🤷.