So the scene that was rumored occurred on Mustafar. From all reports, it was filmed but cut.
In the scene, Ahsoka never left the Jedi Order & was with Kenobi when he confronted Anakin. In this "What If?" scenario, Anakin defeated Kenobi, but then fought Ahsoka & lost. In all that, he STILL became Vader, in both spirit & physically, so it showed Ahsoka she could let go of her guilt for 'abandoning' Anakin & showed her the truth of it always being his destiny.
As visually incredible as that could've been, I appreciate the restraint in achieving the same outcome with the scenes we got. Now she's free.