Hi,
right, that's a bug - it's functionality is 'inverted'.
With architecturalonlymiddle=true the architectural projection will be kept over the whole vertical range and with architecturalonlymiddle=false it will be used only in the middle range...
This will be fixed in the next release together with changing the default value for architecturalonlymiddle to keep existing examples working, when they were only using the architectural setting.
Best regards,
Klaus