While Luke’s actions in the OT happened in confined quarters with no witnesses, his actions here happen in the open in front of many witnesses on both sides with few understanding the reality of what just happened. Luke did not take this action to create a false myth that would destroy the Jedi (what postmodernism would do), but to create a new myth to help rebuild the Jedi.
This is where the case for Luke in TLJ breaks down for me. That his legacy was enacted behind closed doors made no difference to the universe of The Force Awakens, wherein every character’s motivation was dictated by a quest to find Luke, specifically because of the actions he committed to 30 years prior. Rejection of his legendary status would be much more plausible had it been an overexaggerated or a falsified one, e.g. if the world believed he single handedly conquered the Empire with his own two hands and killed Vader, without any redemption or familial connection; but it’s not. Rey, the layman who’s lived a secluded life on a desert planet with little connection to the outside world has the events of the throne room scene in Jedi down to a T. She is our frame of reference for what the majority of the galaxy’s population knows Luke Skywalker to be, which is a 99.9% factual perspective. Functionally the old Luke legend should serve the same purpose as the new & reinvented Luke legend, perhaps even more so because it’s not a trick of the lense with wonky astral-projection attached. It doesn’t serve this purpose because the Director wanted a deconstructionist angle in his film without prioritizing how it would actually make sense in the 8th Act of this 9 Act story.