Yeah, well. Placing whole biomes by hand and placing them by providing monthly figures for temperature and rainfall with code are not exactly the same task.
They are different, but I thought that this method would be, at the cost of being less realistic, easier on the computer than an actual global circulation mode
I think you may be confused. This method is more or less already what SotE is doing. We stopped using a GCM after the Patreon-only release of version 0.1