Mystic weapons *required* for Ultima IV?

Just did my first "solo" run-through of Ultima IV (as in, let everybody die off except the Avatar). Turned out it was way more fun to play without having to manage a full party, and I also think Ultima IV introduced friendly fire to combat (but I could be wrong), so the larger parties were more annoying to manage than Ultima III anyway. Definitely way easier navigating the dungeon rooms when you don't have inaccessible Reapers or whatnot constantly putting somebody to sleep!

Anyway, my understanding had always been that the Mystic Weapons were a requirement to win based on the in-game lore. Since I was using a Mage, during this play-through I decided to hold off equipping it until the last possible moment since it's a melee weapon and I wanted to stick with my Magic Wand as long as possible. Imagine my surprise when I got through the entire Abyss with the Wand and was not required to use the Mystic Weapon at any stage of the proceedings. I am using the GOG version, so is this a bug, or has this always been this way (side note, I did have the Mystic Armor on, as this is always going to be better than cloth for a Mage).