They were said to be Parallel Universes, but since they were Parallel Universes, there would naturally be major differences.
Stephen Strange believed that He-El's existence, as well as his dreams of living the life of another version of himself in a Parallel Universe, were significant differences.
The things of this world ought to be different, yet still arrive at the same destination by different paths.
That universe had a Thanos who wanted to wipe out half the life in the universe. This universe might also have a Thanos, but he might be a benevolent Thanos, or an even more evil Thanos. He might just as well be the same kind of Thanos as the one from that Parallel Universe.
"What is he like? Thanos—what kind of Thanos is he?" Stephen Strange asked impatiently.
If he was the Thanos from that Parallel Universe, then... he would have to gather the Avengers in advance and find a way to deal with him beforehand.
"What is he like? A bandit who attacked Asgard and tried to seize the Infinity Stones." Ancient One's expression turned calm.
She did not know what kind of life Stephen Strange had dreamed of in that Parallel Universe.
She had only opened the door to Stephen Strange's life in another Parallel Universe; she had not fully controlled it, nor could she have controlled it if she wanted to.
Thus, Ancient One did not know what sort of dream Stephen Strange had dreamed.
Perhaps it was a dream of the future Destiny she had seen, or perhaps a dream after He-El's changes. All futures had already become unfathomable, and even Ancient One could no longer be certain of Stephen Strange's life.
The future could only be chosen by Stephen Strange himself.
"You should have read about what the Infinity Stones