I've just had a short look at it.
The original Sustains two modes seems to work correct.
But - Then there also is a HOLD that is active, when the original Sustain is'nt on.
That does hold. But like some other Arturia synths, then notes are stolen from notes where the keys is pressed down, instead of just use notes where no key is pressed, when using more that the max number of notes/ voices.
So the question is, if this is what you mean?