The reasoning for the 1-2 jump squat is that i would suppose ( again ) that in a 'normal' jump squat you can adjust the dip, speed, time and depth, in this 1-2 variation the landing of the first jump leaves you no option, you have to reverse the freefalling and you have to do it fast, a few ms lag and your depth is off. Also i said 'i would suppose' , it was like 2c, just another thing to consider, FYI.
Your info is wrong, kellyb prescribes wave-loaded jump squats too with up to 30%RM.
Jump squats have nothing to do with heavy calf raises and front squat walkouts. Your lower back will have to deal with 100kg plus your upper body weight that are accelerated with 1G for as long as you are falling. That is huge.
And did you really mention a friend of yours that hurt his back doing heavy jump squats as an argument for not worrying about your back in heavy jump squats?
Anyway, once again, i was not trying to tell you what to do, i was offering a couple of options to consider, food for thought. It was more than clear, the first video said 'i would suppose it is a good idea', the second video said 'could be somewhat interesting for you'
And the back...
I don't get why you get so -aggressive- defensive in your replies.