Assuming he was just adjusting a cup, doesn't really seem that big a deal. Being really grossed out by this is sort of pointless, given the sanitation realities of competing in grappling events where no pre-match medical inspections are required.
The stuff worth worrying about probably isn't on their groin. It's going to be on the surface of their uncovered skin. Soles of their feet in particular. If we base "eww" factor solely on the risk of catching something, given the number of people I see walking in & out of the bathroom with bare feet at grappling tournments, performing a figure-four toe hold in a tournament setting is honestly the grossest thing ever.