Slight correction... the PA3X/600 have FIVE fills, if you count the break/fill as a fill. Or four if you don't.
This is two more than the PA2/800, and constitutes a significant improvement in the smoothness of transitions on the new generation arrangers, IMO.
It's a smart move from Korg being requested by players for long time.they have kept same old i3 format(1993) ( 2 fills ) for more than a decade. ( Yamahahave been doing this since psr 2000/740). Now yammy styles (non mega voiced) conversion will be easier and hopefully more to come in Korg style pool ( lack of -which is major disadvantage for Korg arrangers).
Keeping legacy sounds like x3/o1w/i3 alto breath/
strings is also great .triton /m3 /Kronos have abandoned some of the great AI2 syn sounds yet the korg arrangers continues to keep those.