Just a suggestion to take or leave, but I can think of three reasons.
The files would have fewer lines of code. The single YAML file currently has almost 1000 LOC and isn't finished, so I could see it being 10000+ when finished.
It would make finding objects easier because they would be categorized into separate files.
It would make it more approachable for those in AEC that are not programmers.
Suggestion to break up the current single yaml file into multiple files similar to https://github.com/open205/schema-205/tree/master/schema-source files. I suggest breaking the data groups up by major design discipline, which would align it with building drawings and the National CAD standard.