I have never done anything with preloader or cioscorp but I can definitely see why this keeps happening as other people have mentioned.
Even if I know that 60 is the system menu (and some people don't) unless someone told me otherwise I would almost definitely be under the impression that if I installed a custom 60 then my original 60 would be safe.
I might think to myself, I installed custom 60, original 60 should still be there, so it shouldn't hurt me if I just remove the custom 60 to make my system work again.
And it isn't as explicit like it would be in Anytitledeleter "IOS60"
It's just, remove wad? (cios60bf) or whatever