Looks like more of a function of the ferry operators wanting to keep their employees safe by ensuring a covid-free ferry than of the USVI mandating testing. At least for now.
I haven't been on the ferry to know for sure, but based on the rest of Tortola, everyone has given up on covid-free safety here. Very few following the protocols these days. Virtually no mask wearing left in CGB. Active cases at 101 currently.