We never saw Ahsoka die, and saw evidence to the contrary at the end of the episode, two seasons prior to her being saved. Ezra saving her is not influenced by Ahsoka afterwords in any way, so no paradoxes are created, and by extension, no alternate timelines. Ahsoka never died, and Ezra was always going to save her. I don't necessarily think we can rule out the World Between Worlds being used to actually alter events though, we've just never seen it used for that, and Ahsoka actively advised Ezra against trying with Kanan.