Teaching magic spells through weapons

I've heard that learning magic from weapons is bugged, but I took a clean rom and allowed Excalibur to teach Ultima and it works fine. Not sure why people seem to think that. There is text in the item menu that covers up what spell is learned (2-hand), but the magic can still be learned. Perhaps people see that and assume weapons can't teach magic. But even armor is not teaching magic to non-Terra and Celes characters.

Just to be clear, in my hack I'm having issues with, I've made it so Espers DO NOT have a list of spells characters can learn magic from. They only learn magic through equipment. Even though characters such as Locke, Cyan, etc. have their MP displayed, can access Magic in-battle, and can summon espers, they don't learn magic from equipment until after the Zozo event anyway, which kind of negates the point of allowing Terra and Celes to, and mostly negates the point of learning magic through equipment entirely. For testing purposes I allowed Ramuh (the Esper I granted at the beginning of the game) to teach Fire and had Locke equip it. After battles he is learning magic from the Esper but still not from the equipment, which makes it all the more confusing.

Why is it that characters can now learn magic from Espers, but can't learn magic from equipment until after Zozo?

By the way, for anyone else wanting to attempt this, I also found out that in any battle with characters who don't normally learn magic (Vicks, Wedge, Bannon, Ghosts, Moogles), the enemy formations must NOT give MP/AP or the game will crash. This means nothing during the Magitek raid on Narshe can give MP, and nothing during the Lete River event can give MP without making it so those characters aren't in your party.