I checked CBP yesterday and found Puerto Rico and the U.S. Virgin Islands - CBP.gov
but no mention is made of eNOA; but I did see that differentiation was made if entering the US from overseas or a CARICOM country. I'm a bit worried now since I'll be doing that trip in 2 weeks.... Your references are pretty conclusive, but perhaps, hidden somewhere else in the CFRs, there is an exception to the exception. I've posted the contents of this thread on another forum which has plenty of BVI-USVI cross border traffic boaters on it and hope to find someone who has done this trip in the past few weeks to see what the actual procedures are. If one really needs to file an eNOA for this short hop then it is worth updating NOONSITE.COM as well.