I have a totally different view on this...
I don't think there is much wrong with the genetics (which happens to be mostly Remitall), but rather with the way the cattle have been managed.
If you overfeed a young child a high carbohydrate diet with lots of sugar and fat, he'll get obese, he will be heavier than his peers, but most likely less healthy, knee and back problems will be encountered more frequently, etc. Simply put, his body just couldn't handle the extra weight and the heart will suffer accordingly.
Same applies to young bulls, only difference there isn't much bragging rights in saying you've got the heaviest 13 year old daughter in town, why brag with the heaviest 12 month old heifer or bull when the feedsack played the major role and the health and productive life of the animal compromised.
In the same way if you push a young sportsman too hard at a young age they are more likely to suffer serious injury usually associated with older sportsman at a much younger age, Martina Hingis being a good example here.
You can tap a young bull to death (figuratively) as well as work him to death in pasture, if he isn't conditioned to do that it just becomes more likely.
I think 24H is sound, whether the way she was bred/flushed made cattle for the real world (without the open feedsack) is another debate alltogether, I'll leave that for Herefordsire to figure out with experience.