there is no excuse, BUT it is difficult to get the relay work in during the games. most of these guys are all on their own training plan, and it isn't always easy to sneak in a handful of 50+ meter reps at full intensity to lock down the handoffs. Where does Kenny B. fit those full intensity reps in before and after his 200m final? I don't know what his training program looks like.
but here is the problem where you have four guys with 4 different coaches giving 4 different plans based on what their guys have done and where they are going next. and maybe they're dealing with some little niggles and need some rest.
BUT i'll say it again. if they can't put in the work for those reasons, give the job to the courtney lindseys of the world.
and there are guys who can do it and do it almost perfectly without a ton of work. but these aren't those guys.