Oh, high-lining is also used in the US, but the weakness there is the person on the other end of the line has to be physically capable of assisting and also know what they're doing, which, as often as not, they do not, which endangers the piece of meat dangling from the hook.
Double-stropping is a great technique, and it's used in the USCG, however, it's time-consuming, and extremely fatiguing with multiple casualties. Every technique has its shortcomings, and most techniques that haven't been discarded out of hand have their merits.
There are so many possible scenarios for which one can argue for one's favorite technique or other that ultimately arguing is pointless (so is having a single favorite technique, for the most part). A rescue from a reasonably stable ship deck necessitates different handling than one from what was initially reported as a vessel in distress that has sunk and therefore isn't there any longer, or from a vessel hard aground in surf. A vessel with a fairly large crew being fully abandoned should probably be handled differently than a single injured casualty in the water, etc. I don't think there's a single technique utilized by the RAF, RN, or any civil SAR organization in the UK that hasn't been evaluated by the standardization branches in the USCG, it's not like this stuff is a big secret or that the information isn't officially and unofficially shared. It is. We always evaluated each individual case on its own merits and adapted accordingly. The type, size, endurance, and other aircraft and environmental characteristics also play a role in technical development and implementation. What works for a Sea King in the Channel won't necessarily work 150nm SW of Adak or for a Dauphin at the end of its endurance operating in blue water.