I like ROTJ. And find no flaws in the end throne room scene. Vader was continuously growing more and more powerful in the force over time. Who's to say he couldn't mask his true feelings or inner conflict to Palps? Luke is his son and could have a better connection to Vader allowing him to see his inner conflict. Disney has made lots of novels and comic book stories into canon. And many stories have Palps not reading Vader's thoughts or true intentions.
I mean, Snoke on screen seemed more powerful than Palp's, helped merge Rey & Kylo's thoughts with that force skyping crap, yet people believe Kylo could pull a fast one on him? The scene with Vader throwing old Palpy over the balcony is more believable than Snoke not sensing Kylo or the saber turning.
Just look at it this way.... Palps uses the force to see future outcomes/timelines. Like Yoda said "Difficult to see. Always in motion is the future.". 14,650,005 (or something like that ala Doctor Strange in IW
). And only 1 shows Vader defying him and saving Luke. Not the odds to be bothered with obsessing over.