HoMM3 HD is a mod (add-on) for the game Heroes of Might and Magic 3.

Although the reason isn't clear:
You suggest completely banning Guardian Spirits (GS) from neutral creatures – this would cause a lot of outrage.
You suggest fixing the bug by leaving GS in place but resolving the issue of reducing their numbers – people are also against that.
But a simple form of cheating by weakening the guards – turns out to be officially allowed, actively used, and is considered a "feature" (*goat*).

In essence, this is, of course, a bug. But over many years, players have become so accustomed to it that they consider it a feature. (it's like carrying neutral creatures). Most often, this feature is used when attacking a Guardian Spire (GS), because, for example, giants with GS and giants without GS are completely different guards. A checkbox to disable GS solves this problem, but people don't accept this solution; there should still be a small (not fatal) element of risk when attacking, for example, on the first week, against gremlins :D