I think it is obvious that jumping 0-7 is way more difficult than 4-3. You don't have time to rest in-between the jumps and you are already slightly exhausted from the first half.
Yes, and little time for anything more than jump setup, and yet again - there is nothing stopping a skater from doing a 0-7 program if they and their coaching team feel that's the best way to interpret the program.
Many other athletes simply couldn't skate such a taxing routine.
Except a pretty hefty number of the Russian junio ladies. The Junior Nationals from 2018 had 18 skaters:
2 skaters did a 0-7 program, 5 skaters did 1-6 programs (and 1 of them based on protocols I wouldn't be surprised if she jumped her first jump a little early and was supposed to be in the 0-7 group), 9 skaters did 2-5 programs. And of the skaters that did not do a 0-7 program, Trusova's non-backloaded jump was her quad, I think its 4 skaters did all their combos back-loaded section

