Why is there flexibility in clone shape pose (G8F)

TZORG

G8F comes with a G3F clone that matches the G8F zero pose. I also followed a guide for morph transfer which incidentally created another G3F clone for G8F, this one matching G3F's zero pose. Both of these seem to work for autofit without issue. I'm not choosing an outfit type when I test this. Is there something else going on, to make the specific pose not matter? I'm sure that if I made a G3F clone with limbs bent in random directions, it would not convert clothes properly...

(You can substitute G2F or G1 for G3F, above, as well. Same story there.)