If they did this, the game would have to check it he has Loptous (particularly effect-refined Loptous) equipped every time you tried to inherit or equip a dragon skill. I'm no programmer but I imagine that's a fair amount of extra coding to implement when normally it's just "is unit a weapon/move type that can use this skill."

It'd be another story if they made a Dragon Wall/Dragon's Ire type effect the refine itself, they've definitely bypassed inherit restrictions with refines that way before (Caeda's Flashing Blade, Tailtiu's Wrath, for instance) but realistically I don't see them making a whole system to allow one GHB unit to break the rules.