It's not a bug, it's a reinforcement mechanic which basically means you can keep adding more to each building without having to strip it down. Unfortunately, it's not really worth doing at this point, and has led to many players getting caught out by it when trying to produce each tier 3 building.
I agree, there should be a way to distinguish between each tier of building, and also perhaps have reinforcing buildings as a different blueprint to building them in the first place.
~A~
15-Feb-2023 19:17:46