I think it's not quite that simple - I'm not only experiencing the same glitch allowing buildings to be placed over nobuildzones in some places, but there are also sections of my planet's build screen without nobuildzones which are acting like there are nobuildzones present anyway. Maybe the nobuildzones are being shifted out of sync with the graphics rather than just being nonexistent?
https://imgur.com/a/YpiuAwCFurthermore, I've verified that - to a small extent at least - building over nobuildzones can happen even in the original/unextended part of the build screen at the very top left corner (confirmed via presence of the builderbot in rotated idle pose), although this is still on a planet where my build screen has been extended both eastward and southward...
https://imgur.com/a/SrK427e