According to Lucas, he had time and money to do 3 squib setups for that shot. Each one went off with bad timing. He said in one shot Greedo shot way before Han, in another Han shot way before greedo, and in the one they used, they both went off at about the same time, but you couldn't really tell that. He didn't have time or money to do more setups, so he decided to live with that and try to make it clear through the dialogue that "the idea" was to kill Han.

Didn't Tolkein rewrite his works for future editions? Did he also re-publish his previous works along side his new editions each time?

I don't see the difference here with what Lucas has done.

If this is all just "commercially driven rubbish" then why are any of you trying to preserve it for the sake of "artistic history"?