I would argue a prime LeBron is/was harder to stop than Harden but Bron doesn't seek out contact in the same way Harden does. What I mean is Bron doesn't try to bait you into a foul and not care if he makes the shot or not every other play like Harden. He hasn't built his game around trying to get to the line. Now he does get to the the line a lot incidentally because he's a tough cover and sometimes all you can do is foul him but that's not that same as seeking contact.
But I digress. I can't convince you that there may be reasons to explain Harden's insane FT numbers other than "superstar treatment" (minutes played, driving to the rim, seeking contact, hard to stop, shoots a high clip, blah blah) so I have to ask you, why James? Why is he the ONLY player who gets superstar calls. Is it because the Houston Rockets are America's team? Because James is so universally loved by fans of the game? If the numbers aren't based on contact created on the court, then why haven't owners and other players/coaches expressed outrage over this blatant favoritism. All I hear opponents say is what a tough cover he is and how he's so good at creating contact and making people pay for reaching/swiping. I feel if there's this blatant a bias people in the NBA (not is fans) would be in an uproar, certainly not praising him and he CERTAINLY would not be the inaugural players choice for the MVP of the league.