I took your advice and reached out to Stan Hieronymus directly. Here is what he had to say on the subject:
As in all things brewing there is a certain about of "it depends." I didn't ask the Trappist breweries if they had experimented with other conditioning regimens, just what works. Certainly time is a consideration - Rochefort, for instance, has little room for conditioning and wants to move beer through pretty quickly. Westmalle has plenty of room, but is very focused on making sure its beer is the same - so has picked a process it can dial in. These obviously work well for them, but . . . at Schneider Weisse, and somewhere different than several other German breweries, the condition beer for a week at 70F and then two weeks at 50F because they prefer the flavor development (mostly ester-generated flavors/aromas of fruit, including banana).
Another factor in the "it depends" is cellaring after conditioning - how long and at one temp. I like to store my beer at 50-ish, so it's going to develop in the bottle.
One other note. Bottle conditioning will create diacetyl that needs a warm rest. That's likely one reason the Belgians go for the consistent, rather warm conditioning.