No, the code was rewritten quite recently, between 0.3 and 0.4 build, with specific intention to allow for above ground z-levels. There is nothing “pseudo” about it. Below ground floor are mapped to z- layers and above ground floors are mapped to z+, where ground level is at z=0 layer, exactly how it should be.
This is one of the reasons why they don't want to include more of it; the system that Whales utilized is intrinsically faulty for the purposes that they would like to utilize it for, and thus must be written.
They are already including many new buildings relaying on the same system. It’s not faulty, it does what is supposed to do. There is no any difference whether new office tower will have a garage above or below ground. If one works, the other works just as well.
As for my logic, I would like to point that the claim that reasons not to increase utilization and those to continue current utilization are two completely different things. Your statement that "any reason to not have above ground z-levels is as good reason to throw underground levels from the game" would be exactly the same as saying "any reason to not use cars more is as good a reason to take away your current cars".
In a way, yes. You wan’t office tower to have underground garage, it makes the building more interesting, right? Then explain why do you not want church bell tower, would it not make church more interesting?
Just because a reason is valid to prevent further use of a system (in this case because said increase would not be worth the extra work later [1 bonus - 2 work = -1 total]) does not mean it is a valid reason for the removal of the system without a replacement (since the current implementation requires no extra work penalty regardless of if we remove it or leave it in, meaning the balance now favors leaving it in [0 negative - 0 work = 0 total vs 1 negative - 0 work = -1 total]).
Yeah, if it was not for huge contradiction, in that they are actually investing in the said system right now with all the new buildings being added. Those new buildings could have upper floors just the same as underground floors. It’s only a matter of drawing them on the map, or not.