Now he is watching his OL do what Nebraska fans have been doing since he began coaching the football program into being a non-factor...throwing up!

Rhabdo can cause vomiting but vomiting doesn't cause rhabdo and is not necessarily related at all.  Rhabdo is caused by the destruction of muscles due to overworking the muscles.  Vomiting in workouts may be caused by dehydration or lack of sodium in the blood but can also just be due to intense aerobic exercise stressing the digestive system and be relatively harmless as long as the athlete rehydrates.

Unless they have rhabdo or some other serious condition, it's extremely unlikely that someone will vomit more than once in a workout if they aren't rehydrating properly.  There'd be nothing in their stomach to vomit.

Muscle destruction/rhabdo usually comes from excess load-bearing exercise.  Vomiting comes from intense cardio / aerobic exercise.  It's common among all kinds of athletes but most common among marathoners / ultramarathoners / cyclists.  I'd not necessarily consider it a bad thing among OL athletes if they are being monitored and are hydrating properly.  It may mean they are working a lot harder on cardio conditioning than some OL athletes do, and that might be a good thing both for their performance in the second half of games and also for their long term physical health.

As a general rule, you don't vomit unless you are pushing really hard on the cardio side of things, and that's rarely bad for your health.

I'm not an expert on this, but I know something about it and I've vomited loads of times in workouts.  I'm not going to say that all is fine at Nebraska but if they are keeping a close eye on them then Frost may be right in seeing the level of effort as a good thing.  I'd rather have offensive linemen that at least throw up occasionally than those that don't want to push themselves hard on the cardio part of the workout.

There may be something to what you are saying about advances in knowledge and again, I'm not an expert.  I can only talk to what I've known in the past.

With that frame of reference, unless we're talking about something really bad like rhabdo, and I'm giving the benefit of the doubt that they are now clued in and on top of that, the only thing it really means is guys are pushing their limits on cardio work.  You can vomit when you are out of shape, or you can vomit when you are in top condition.  That just changes where the limits are, but you can still push your limits.

You don't want to be going that hard 2-3 days before the game (or a race, or whatever) but you might well do it Monday or Tuesday in-season if competition is on Saturday.  If I had a guy vomit on Wednesday I'd have him ease off for the rest of the workout but if it happened on Monday I'd make sure he hydrated but if he felt he could go more, I'd let him.