i think it's about , ultimate raids weapons/titles , as you can see
people do old ultimate for the titles/weapons , at least most of the players who do it
so having it unsync will take away the difficulty part and will make this rewards a normal thing , and that is what SE don't want to be , and you can see that in the savage raids , you can solo o4s as a tank
let alone Ultimate raids is made for the sake of team work , if 1 person mess up in some part , it's a wipe.