To me, it is the yeast profile. If you brew a pilsner only beer, it can be either a boh pils, german pils, kolsch, saison or belgian golden strong; some would argue a cream ale too. The main (not only) difference is the yeast.
That said, with the yeast flavors being highlighted with these beers, IMO, you have to be very careful with your hopping and grain bill or it just becomes muddled. Too many flavors are (can be) clashing and it gets to be too much. Ommegang and Stillwater, however, are doing great things with darker belgian style ales.