How much of the total volume of the device was the case/housing?

I suppose the glue-everything approach is partly due to the desire of making a device very thin. There's no room for strong, load-bearing outer case, the internals are load-bearing.

Honestly I'd expect that to be SIGNIFICANTLY easier to waterproof than a laundry machine. Partly because laundry is sometimes done warm, and warm softens materials (like gaskets), but mostly because laundry has surfactants that considerably reduce surface tension, making it far easier to slip past gaps.

There is a good reason waterproofing claims are specific about the kind of liquid (usually just fresh or salt water, usually without significant movement (i.e. jets, like you get in a shower)).