Well, my recollection is that the minotaur was the original big bad, and the lich was added when it was upgraded? But maybe I have that backwards. Anyways, if the minotaur is there and active (and not a relic) I will change it's scripts so summoning one elsewhere won't break the HB questline.
I think you are correct in that the Minotaur was there first, and then the Lich was added. At least as far as I remember. My last time in Hickory Branch featured both of those NPCs.
My guess is that I missed the original version with the Minotaur, and only came in when the Lich was already there...
Ok, here is an updated Fiendish Minotaur script, I haven't tested it in situ but I did test that it works both for summonings and for the regular guy and it seems fine. It goes in data/scr obviously. Not really important unless you plan on throwing around Greater Planar Ally before clearing the Ranch. Earmarked for my basket of fixes.