You're ignoring a lot. I'll try to explain one more time.
If the weapon's function isn't based in mass like swords usually are, then it makes sense the mass won't be held in it. The gauntlets follow this and you bringing up another sword does nothing for your point.
Her being trapped is a massive anti-feat I won't ignore that but that's a topic for a different time. And I reread the fight, Yoru
stops FD's attack, this requires LS comparable to FD, who is listed as Class G. There's also the 606 sword, for some reason that is listed as Class G, but I don't get the logic there either. When swinging a sword, the sharpness only matter if you swing it hard enough, otherwise no cutting happens. So Asa's feat with her room sword, unless I'm missing some scale chain that make it superior to every other sword, would mean that's just Yoru's strength that breaks her free from the otcopus.
So no, the mass of the sword has no reason to be reduced because a gauntlet doesn't have the mass of the devils used, the weapons' functions are different.