My suspicion is that its under the following constraints:

1) Site is cleared, maybe foundation complete (which means excavation done etc) 2) All prefab pieces are done 3) No restrictions of number of people on site (besides physical realities)

#3 is no small case. I've often noticed that construction companies in the west have very few people on site. Certainly not 50 people per floor, for example. IMO this is due to wages and contracts. a) wages are too high to risk idle people and b) contracts are insufficiently written to incentivize speed of delivery (probably in favor of cost).