Well, just to bring up an exception:
U.S. fishing vessels up to 5000 GRT can be operated with fishing vessel deck officers licenses of the appropriate tonnage.
Seperate issue:
Another way of looking at it is this: U.S. ATBs of <300 GRT are apparently pushing barges of <10,000 GRT, and doing a pretty safe job of it. I’m not hearing about a large rash of accidents involving such vessels.The rest of the seafaring world may surmise it is stupid, or it is equally valid that the rest of the seafaring world must admit that unlimited licenses are proven to be unnecessary on vessels up to 10,000 GRT.