I don't doubt your experience or think you don't know what you are talking about. I am just speaking from my experience and still being in the thick of doing a custom infill.
If his GC has 2 builds side by side, one will be ahead of the other, always. Unless he gets 2 framing crews, 2 roofers, two drywall, insulation, etc crews. One for each house. I watched my GC chase and chase. He is still chasing shit for me and I've been in my house since the beginning of March. I don't envy that shit. This is my backyard as of 10 minutes ago. These guys were supposed to be here before Canada day. Today is day 1 of concrete hardscape. Again, just my current experience talking and no slight to the Jr. cool Dude.