I agree with most things here, it is just a topic that has been over-analyzed.
Imho, the supra-maximal half squat(HS) is more GPP than SPP. And all rules that apply to supramax partials apply here too, it is that simple.
But there are the sub-max explosive variations, those are more 'jump-specific'. I will agree with you that absorbing the landing of a depth jump(DJ) is both more specific AND more 'heavy' than a HS, given the short time window you have to absorb the forces of the DJ. I will take it a step further and say that maybe the DJ is heavier by terms of load too, regardless the speed: If i remember correctly landing from 1m equals above 3 times your BW , so the equivalent load for a HS would be over 2*BW. No references or accurate numbers here, just rough approximations to give a sense of what we are talking about.
The concentric part of the HS is nor replicated in the DJ though. The DJ is an unweighted jump, while in the HS you still have the bar on your way up. But again the DJ is faster. So it is not about choosing DJ or HS, they are both very useful tools, the way i see it DJ is more speed-strength, HS is more strength-speed.
Another factor to consider ( and that is where adarqui's 3*BW chasing comes in ) is that some people have issues with full squats. Adarqui is one of them, whenever he tried going heavy on fulls he kept injuring his hip, that is why he changed to halves. But now we are talking GPP. Regarding GPP, kellyb also favors the full over half squat:
http://www.higher-faster-sports.com/squatdepth.htmlI typically don't recommend half squats except for specific phases where the use of partials can be used to peak out strength. In my experience the average trainee who switches from half squat to legal depth squats will gain a near immediate 2-3 inches of vertical jump increase just by taking their squats thru a fuller range of motion, even with a significant lesser load. As a personal example when I first began training seriously I trained for a good 3-4 years performing half squats because I didn't know any better and half squats are what we were taught in school. When I learned what a legal squat was my poundages went all the way from around 300 down to around 185, BUT despite the significantly lesser weights I started making really good vert gains and gained quite a bit of muscle on my thighs. I've seen the same thing happen in countless other trainees.
But he also mentions there are exceptions:
However, SOME people can't achieve legal depth without their lower back rounding no matter what they do. Many tall people fit the bill here. These people shouldn't push the issue. Just squat to whatever depth you can while maintaining your natural arch.
If you ask me, and i have been a GPP-half-squatter for a long time, the best bet is to use full squat for GPP , DJ for RFD and HS at limited time periods for peaking.
2c