Why is this done?
Generally I wonder if buildings still render icons. E.g. if a building has both building=yes and shop=supermarket it should render a building with a supermarket icon on top. Note that this is different from the (also commonly found) shop=supermarket node inside a building.
Previously building icons were accomplished with the code around m_buildingStyles[category]->iconStyle() above. Rendering itself was then delegated to PlacemarkLayer. The rendering should still work even when the building visual category is gone, does it?

Hmm, so do you mean that we need to keep the

setVisualCategory()

call or do we need to restore the removed line# 1306?

I think the isBuilding check is not needed here. And generally i wonder if building icons still work after the patch series.