I've rarely (maybe never) met a tugboat engineer that was incompetent at anything other than maybe paperwork. Sometimes a new academy graduate would try and not be able to handle being the only engineer onboard.
I met a fair number of "engineers" on OSVs that didn't deserve a license. They probably couldn't even handle being a PIC on a tank barge and pumping cargo was their most important job. I had no faith in many of them to actually fix anything if it was necessary, and I hate feeling like that when I'm offshore. The most incompetent ones got run off the boat, but it was basically impossible for anyone to get fired (before this downturn) so they were dumped on another poor crew that hopefully wouldn't complain to the office as much about their ineptness.
Don't put so much faith in the honesty of the US Congress. The oil patch companies bought themselves these bullshit licenses so their $%@&@-$ officers won't have to take a real test or be able to leave and go work on a real ship (or drill ship) so the company doesn't need to pay as much.