Just overheard the commentators on the Euro channel Sports live stream for the European Champs in Glasgow and they questioned if the judges actually enforce the 15m rule.
They did not mention the strokes but said they talked to an official and that an official wanted to disqualify a swimmer for going under water beyond the 15m mark and that the official was overruled by most likely a referee and the request for a disqualification was rejected, what the commentators found horrifying because being under water beyond 15 is an advantage.
Well, strictly speaking officials should never discuss such matter with anybody and should always refer any enquiry to the referee.
Well, I looked if all the 15m mark lane ropes are lined up across the pool and they seem to are from my viewpoint.
The commentators did not say which stroke they were talking about because in the breaststroke the 15m rule does not apply.
However in such televised events, it becomes pretty obvious if strong failures to comply with the rules are not being noted by officials and everybody watching is horrified. Cameras can pick up such oversights but it often depends on the viewing angle.