Why 'Workout Confusion' Leads to 'Results Confusion'

There are a lot of different workout protocols out there that are based on, more or less, confusion. By keeping the body constantly guessing, the idea goes, it never completely adapts, and is constantly progressing. This can be as little or as much random activity as you like – everywhere from just picking different exercises every time you work a bodypart, to doing completely random workouts, with no set protocol to it.
There is a certain amount of validity to this. However, I feel it can be taken too far. At some point, you go from “keeping the body guessing” to “keeping the body confused.”
Think of it like this – say you were studying for a test. You could re-write your notes, re-listen to lectures, make flash-cards, etc. Now, if you were to mix and match all these different learning styles, that might work if you were studying for one test in one subject. However, apply it to a different test in a different subject everyday, and you never really study enough to retain like you should. Sure, you'll retain and remember some of the info, but not nearly enough as another method of studying might let you do.
Well, random training treats the body the same way. You need a certain amount of adaptation, so that you can progress on your training.  This is what allows you to get stronger, faster, build more endurance, etc.  You have to have a planned form of progression, which means a planned set of workouts.  By repeating workouts (or even simply a style of training), you expose your body to the same stimulus, which let's your body adapt and improve.
You need to lift heavy weights in order to get stronger, right?  Well, say one guy benches heavy once per week for three weeks.  Then say another guy also benches heavy the first week.  But then the next week he does dips for maximum reps, then the third week, he does pushups as a part of circuits with other bodyweight calisthenics.  Who do you think is going to get stronger?
I once read a professional strength coach (I'm not sure who it was) write that (and I'm paraphrasing here) “Anybody could beat the hell out of their trainees. It takes an intelligent coach to make them better.”
I agree.
Train Hard, Rest Hard, Play Hard.