I think we need to go to the extremes here to make a point. Ask it another way:
Athlete A is 300 lbs in BW, squats 600
Athlete B is 150 lbs in BW, squats 300
Both have the same ratio, structure, CNS etc. Who jumps higher? I would say the 150 lbs one, because it takes less effort to change direction at that weight and there are other things like, again, the absolute force that you can transmit through connective tissues that is important too. These things are being monitored by the CNS all the time for safety reasons (mechanoreceptors, proprioceptors etc).
So imagine the 150 lbs guy going for a high speed jump with a let's say 8G plant.
That's 8Gx150 lbs = a 1200 lbs force in the amortization phase that is transmitted through the skeleton.
Athlete B tries the same thing, at the same speed, and gets himself the same 8G plant. His skeleton, connective tissues, tendons etc need to deal with 8Gx300 lbs = a 2400 lbs force in the amortization phase.
So Athlete's B connective tissues need to sustain a tremendous amount of pressure and tension without the CNS raising red flags for safety reasons that they might break, regardless of the fact that they both squat the same 2x and muscularily produce the same amount of force/eccentric force etc.
It's like taking a tractor and trying to make it a race car. Sure, you might design an engine capable of revving and pulling the tractor at a racecar pace, but the joints of the car themselves, the materials themselves, the wheels, the articulations, the suspensions etc would just fail at those extreme tensions and forces being applied at that weight.
And if the tractor has a very good computer that senses all that, the computer will shut down the power to prevent the tractor from breaking down.
In my opinion, that's what's going on with the bodyweight in a human when jumping, that's how it acts.
And it's even trickier than that - we are looking at squatting here. But usually we increase our squat and bodyweight (say we keep the same ratio) but the calves don't get that much stronger. And then the calves, which don't grow as fast/strong, remain behind with the squat going up. That changes the mechanics/overloading of the jump, making the quads do the breaking more, which makes you more quad-bound, which makes you increase the knee bend more, deactivates the hamstrings more, the angles are different and on and on and on.
So it's more complicated than simple numbers here.