As Slast has pointed out, the Canadian rules are "sus" in this area, apparently allowing descent without seeing the actual runway/PAPI.
Indeed; if reported correctly, they seem to be. However, even if allowed, I ask who would feel comfortable descending in manual flight below DA without the target insight. Scratching around at low level, on your own in a spam-can with ground contact at 80kts, is one thing. Descending semi-blind in a pax laden medium jet at 140kts is quite another. I'm not talking from legality it's from a self-preservation aspect. I'd be scared poo-less.
Regarding split crew duties, even MA's, it is human nature that PM, below DA with visual references, would be head in/out. They would confirm that the visual queues were correct & performance parameters were correct, but also that the visual flight path was safe. It's a glance in/out that would not reduce significantly the PM instrument scan. PF would be more out than in, PM doing both.
Regarding the hotel illusion: If that was the perceived target for visual profile, vertically, how/why did they descend so far short of that? PF did increase the ROD, but as with any landing the touchdown target is kept stationary in the window. In this scenario that could not have been the case, and for quite a long time. It must have been very scary wondering when the 'expected' runway really was going to become visible. It is a human trait that a pitch down when visual with approach lights in low vis is not uncommon. I once called a GA in a biz-jet, when the captaining was 'pinching a bit' at DH and did just that. Like I said, a bit in/out <DH. Glad I did; long before GPWS.