I’m a bit out of my depth with that one but what I do know is that modifiers in Blender technically generate a new mesh after every modifier. That’s why they can be so slow on complex objects. So, when there are no modifiers, Blender is able to use instancing while rendering and in the viewport to speed things up. When there are modifiers though, that efficiency is lost since the mesh that gets passed to the renderer is different. Technically if both objects have the exact same modifier stack then they should be able to use instancing since the mesh that’s passed to the renderer is the same, but I guess that’s an optimization that just hasn’t been made yet.
