we're not running breweries, so what is done on a commercial scale doesn't apply to us. huge cylindro-conicals with hundreds or thousands of barrels of liquid in them are going to behave differently than our 5-gallon carboys. for example ester production is quite different under the pressure created by a 20-foot column of liquid. BMC's go grain-to-bottle in less than a month, doesn't mean that you can complete a lager in that time.
belgian yeast work slowly on a homebrew scale - especially when making big beers like a tripel. in my experience they munch through 90% of the sugars in the first week, then even longer to finish off the last 10%. put in some time for them to clean up, for flavors to meld and even out, and all of a sudden 4-5 weeks doesn't seem so crazy. you could bottle after 2 weeks, but i'd be concerned about potential over-carbonation and unevenness across the batch.
and this is a purely personal and philosophical thing, but belgian beers aren't meant to be rushed. the goal of making a belgian is to make the best possible beer. you should cut no corners. the monks that make the beers we love so much aren't in a hurry, why should we be?