Well contributed, The Luke. Yes, animal studies are not always applicable to humans. A pity the scientists aren't doing more bodybuilding experiments on humans.
There is no need to go to failure. Well, I advocate doing as many reps that you know you can complete. Then rest and do more sets.
I am aware of the physiological fall-off in reps when training with maximum loads. That is why I superset with another muscle. Biceps and Triceps for example. Then to maintain a target rep range it is necessary to rest a bit longer between sets. Once you get the rhythm going it is possible to keep the reps around 7 or 8 and still do the maximum resistance. The trick is to select a maximum that you can do for about 15 reps. That is after several higher rep warmups. When the reps fall to 8 that is still sufficient to be safe and also trigger hypertrophy.
In practice, I usually recommend doing about 5 or 6 maximum sets. No one has done this for squats yet! Too damn hard. However, what would happen if they did such protocols.
I am aware that the repeated bout affect has a lingering presence in the muscles. All the more urgent, then, to avoid that adaptation and keep the muscles sore.
It is just speculation about all day training. It may or may not work. I think it would but I am not that confident. In the meantime, there are many sub-maximal routines that will be almost as effective. What worries me is we might miss out on possible hyperplasia if we persist with conventional training.