True, and judging by the story conference transcript excerpts it doesn't seem that too much was meant to be read into the scene. Perhaps Kasdan played it a little darker than Lucas intended.
I'm currently going through the story conference transcript excerpts between Lucas, Kasdan, and Marquand. It's interesting how argumentative Lucas and Kasdan seem to be--Kasdan seems to object to a lot of Lucas's ideas and vice versa, while Marquand tends to be a mediating voice.
Kasdan also has trouble detecting when Lucas is kidding around. For instance when Lucas suggests that Luke should put on Darth Vader's mask and declare himself Emperor, Kasdan says he likes the idea but Lucas is actually horrified that he does.
Kasdan really wants to kills off a hero--possibly Luke, so that Leia is left as the sole Jedi, or possibly Lando. Lucas objects strongly to this, criticizing Kasdan for being "a product of the 1980s" and arguing that movies don't need character death to be emotionally powerful.
(Kasdan also rather bitterly suggests Lucas may have "misled" Billy Dee Williams into thinking he would have a greater part in the third film due to Han Solo being stuck in carbonite.)
Re: Luke's "plan" to deal with Jabba, Lucas suggests that Luke's overall goal was always to lure Jabba and his cronies out on the sail barges over the Sarlacc pit, where they would be trapped in a confined space. Thus Luke and his friends who had infiltrated the palace could take them on more equally. Bargaining for Han's life was not the primary plan, but it would've been a nice bonus if it actually did work.
Lucas is having difficulty fitting an explanation into the film of how Luke built a new lightsaber (or "lazer sword," as the transcript consistently refers to it.) Kasdan suggests it should be a different color blade. (This idea would not be implemented until post-production, when the originally intended blue saber color showed up poorly against the California sky in the sail barge scenes. The change of color moreover allowed Lucas to delete the rather poor-quality expository scene earlier in the film of Luke completing the saber and giving it to Artoo.)
Lucas notes that it was Obi-Wan who cut off Anakin's right hand during The Duel on the volcano planet. That was how Ben got Anakin's saber to give to Luke; Vader cutting off Luke's hand was thus an act of symbolic revenge. (Anakin then lost his other arm and his leg when he fell into the lava pit.)
More to come....