Agree having separate large textures for every channel including roughness, reflection and normal for every object in the scene is unnecessary and use large amounts of GPU memory and slows down Eevee. It is specially important to be efficient in large scenes with hundreds of materials. This is one of the good things about your “Definitely EEVEE Materials System”.
In windows facing the outside even when the environment is bright I do use some reflection. I like to use “thin glass” shader by using my glass shader setup and replacing the “Glass BSDF” node with a “Transparent BSDF” node. Objects close the window will reflect back into the window. This gives a more realistic interior. What is not needed is refraction which can cause some Eevee artifacts.
Here is example of using small amount of reflection on a window from my one of the scenes from Chocofur from my “Realistic ArchViz” series see the link Window Reflection.
