the original sombra from the crystal empire, the one that discord summoned, and this one that Arrhythmia (evil cadance) summoned? all different sombras. the real sombra got reformed as per the comics, the one that destroyed the tree of harmony is based off of discord’s recollection of sombra and what he imagined he was like as well as the stories told and whatnot. this one is based off of cadance’s memories of him which combines the original and discord’s version as she dealt with both first hand. thats why they all act so differently.
its probably not an uncommon headcanon but, yknow, worth mentioning.