Feckless (in modern usage) tends to imply lack of responsibility with obligations to others.

They're not really obligated to have any boomers for NATO or anyone else. NATO policy flat out says that the US is the deterrence backbone. The rest only supply token assets to show unity. Although I''ll give FR credit for going beyond the minimum.

You also actually only need one boomer at sea, and you only need a perception that there's a good chance that it will work. Nobody is going to press to test hoping the opponents launch system fails. If the launching part works, then it's game over, the Trident D5 is a US weapon and it *will* function once properly launched (and the bad guys have no illusions about that).

The weapons themselves are selected at random from a common US/UK pool... they get literally the same ones we do (LANT Fleet anyway).