Oh I've read that before from the wiki as well as some of Philipk's and the Unreal engine articles on the subject and such. A lot of tutorials and information out there don't really talk of cases that I had mentioned though which extends onto designing how wall are set up or having contact points beyond just the sides that tile(that I thought would have been a possible solution for "who gets the 'window'".
I don't see a lot of material on designing concise modular pieces for interior/exterior environments beyond some sealed-in interior or placing rocks around to recreate a cliff face. They tend to account for an only-exterior or only-interior but not much that are similar to some GTA-like environments.
The original idea I had for this environment for example was to have these inner wall pieces with windows that never escape the 500x500x500 module grid "cell".
And the outer side of the wall would just be its own module that would make use of some "window contact point" that would favor the interior piece to have the window geometry.
Only to later extrapolate that this would involve making small convex corner wedges for each wall type and is almost never seen from the interior besides possibly the window sill while still demanding an extra drawcall which is when I figured that just giving the interior wall the entire window piece would be better but this tug of war of who gets what
is eating away at the previous information on modular environments I've used.