It’s not so much that you shouldn’t be able to do it as that there’s no way we can do it without a permit.
In the original post, he's sloped the new roof back towards the house - huge issue where I live (Atlanta - we got a lot of heavy rain) since that's going to cause water entry in the basement or erosion on the foundation.
It can also be a fire hazard in many situations. Ex - in my area there's a mandated 10ft gap between the property line and any structure. It's there to prevent people from building right up to the property line, essentially creating townhomes, but with none of the fire/safety planning those require.
All that said - I agree with you, this code is likely there to discourage people trying to skirt around inspections (and because it's easy to spot).
Previously lived on clay soil above the freeze line: everything needed substantial gutters and routing away from home.
Now live in sandy soil below the freeze line: most people don't even have gutters.
So for new construction or reno, absolutely follow code! Why not?
But for old construction that doesn't have obvious dangers and has served its purpose across decades? Why fix what ain't broke? It's entirely possibly it's a perfectly viable alternative solution.