I've found that these houses repeat themselves only at the outer town zones, after the town grows enough to get a fourth zone. If I disable swedish houses, then a lot of the TTRS banks take the red houses place. I'll take a look on town zone definition for these buildings.
Zone 1 seems to be the real bugger. Only a few houses of each set are allocated to that zone. On the example of swedish houses, only the red house with dark roof is available before 1920, because all the others have garages (people didn't have garages to keep their horses in the 1800s AFAIK). Tried NekoMaster's idea by enabling the sets to keep the original houses and very little difference was perceived.
What I saw on the NFO code was that property 13 on action 00 (which defines the houses) has the job of assigning town zone. For example, the red spamming house has the following line for availability mask:
13 03 F8
That 03 seems to be the inner suburb zone, but what about that F8?
Here is the swedish houses EarlyMod code I am using:
swehousesEarlyMod-source.7z [914.37 KiB]
Downloaded 8 times
Any experienced NFO coders have any advice?
P.S. I am working on another NewGFR and I'm so glad NML exists
(NFO can twist an untrained mind like mine)