It's not failure to retire, it's failure to respect.
The way I see it is that delay restart is where a player tries to prevent a restart being taken or takes so much time tha they are clearly delaying.
Failure to respect is for scenarios where defenders refuse to move back to 10 yards at referees orders Or once at 10 yards encroach on the position of the restart e.g. Creeping forward or charging down from the wall before the kick is taken.
Agreed, I put it down as either, but in a recent education presentation the speaker referred to standing at the ball as a delaying the restart. Probably the correct one is failure to retire distance, but I don't think anyone's going to be fussed?
Running up and standing on the ball (ie, not letting them even have a chance to put it into play) is delaying the restart. Running up and standing a couple of metres/yards away? Failing to respect the distance.
The difference here:
Can the team with the free kick actually put the ball into play? If so, Distance. If not, Delay.