Actually I remember the discussion now that he brought it up - Hydro DID want city size to not update whether the autobuild should be there for much the justification Joe gave. It was considered.
This is not a design choice per say, more probably it is lazy dll programmers who never bothered adding in the new types of requirements in the code that decides if a building should stop functioning in a city.
How are the lazy dll programmers to blame for design choices made by xml modders?