I don't see what rule we could use for that. From the plugin side, a building or a surface is just a mesh with many faces.
As RealViz suggested, in these cases the best option is to assign by name.
Hi, thank you for the response, I was also thinking about that. Maybe when a surface consist of more than X amount of elements, there could be a warning. Because it's weird: why FP would make Max not responsive in this case. The geometry might be 'complex (consisting of multiple elements) but the total surface area is a smaller than most surfaces I use to scatter grasses or anything. So there shouldn't be that many items. Not sure why it would make Max hang.
As for RealViz's tip, I isolate most of the time before assigning instead of the assign by name option. I don't have this a lot, might have been the 5th time in 10 years. I was just wondering why it would hang Max and if this could be prevented.