I guess blizz didn’t want people to farm them out of the GR to pwn the boss super fast. Also, if they follow you from floor to floor, then once again a zdps could solo a 150 just by pylon jumping.
Basically, once again, we can’t have nice things thanks to a few cruddy players.
They already made it so that any active clones are dismissed upon entering (or re-entering) a GR, even if those clones were generated inside the GR.
No they couldn’t, because even if you get a pylon right at the entrance, the clones aren’t able to kill mobs at GR150, so you’d never get enough progress to even generate a second pylon, let alone have all five at once. Clones certainly can’t kill GR150 guardians.