The issue is Ahsoka. I like her, but Vader’s line, “when I left you I was a learner, now I am the Master,” indicates Vader was never a Jedi Master as Anakin.
Or a full knight for that matter. Just another bit of OT continuity Lucas either forgot or ignored when writing the prequels.
Indeed, a good place to have had Anakin fall was The Tuskan Slaughter in AOTC. For then was still a Padawan Learner.