That's exactly what it is. Can't dispatch if landing weight is above single engine, ice penalty applied wave off ability weight limit if known freezing precip... Or something to that effect. Not sure if it applies to other Boeings (I've only flown the guppy, it has no tail anti ice), but Ive seen as much as 10k lbs.

811 would be a brand new 900ER.

In the event they filled it, you iced up, lost an engine, and had to wave off.... You woulda been screwed! Otherwise it's a great airplane 99% of the time. Just takes forever to load/unload. Had 188 SOB one the other day.