It’s got naff all to do with being “technically right”. IMO they are just two blokes trying to ride along that road in what they regard as the safest possible manner.
Come on, do you really believe they had the conversation that went something like : “We’re on a busy road, it’d be best if we ride two abreast to make sure no-one hits us” ?
Ridiculous. They were being selfish.
Ride defensively, ride assertively, but above all ride considerately.
Antagonising motorists, and I think WE ALL KNOW that this will antagonise them, is always a bad move.