I'm not sure whether and to what degree this module uses LA synthesis, there is some talk about a "cut-down version" of it on the net. But if you look at these soundfonts that are floating around the thing about them that sounds most blatantly wrong are often the reverb/chrous effects. To get this dead on the whole synth engine, DSPs etc would need to be reverse engineered.
Even though Munt seems to be quite accurate at this point there is still a discernable difference compared to the real thing. It all boils down to the developers not understanding the hardware completely due to Roland protecting their IP.
It actually is possible to recreate a hardware MIDI synth very accurately if the company behind it decides to do so, Yamaha's softsynths are the best example here. I can't recall hearing any differences when comparing DB60XG to S-YXG50; with Roland it's a quite different story. Guess they didn't want to jeopardize their sound module market too much, after all they are putting out these things to this day...