Does it become a safety issue? Some people have trouble doing heavy weights on the leg extension.
Also, perhaps because a front squat is more similar neurologically to other "real world" movements, there might be more crossover in regards to the actual events.
Otherwise, your logic sounds like a good one to me, but I must point out that is does contradict in some ways your thoughts in regards to your Muscle Meets Magnet related theories. If certain excersises train only certain parts of the muscle, doing the leg extension (for example) wouldn't really be as helpful in producing a bigger squat. It seems your question goes against your supposition.