The halacha regarding a small, thin negiya (kechut hasarah) between the left regel and gug of a hay is well documented. Scraping is prohibited and considered chok tochus. This is in stark contrast to other letters in which such a negiya is fixable, for example where two roshim of a shin are connected with a thin line or the yud of an alef is connected from the other side as well as the yerech.
It seems the hay is more chomur because with such a negiya it can become a ches. However a thin line connecting the left side of the bottom yud of the alef or two heads of a shin are less problematic because in both cases its still clearly an alef or a shin.
So why then do we rule that a kuf, where the left regel and gug of a kuf is connected by a thin negiya, that it's outright possul like a hay. Surely it's still recognizable as a kuf in the same way other letters that have a thin negiya without causing a shinuy tzurah. Why do we treat it the same as a hay?
I never understood this and if anyone has any svaros / mekoros I'd appreciate it.