Wind Main's breath attack, Mifune's mystery, Nagato's mystery, etc.

The shield is dispersed, buffs from passives are supposedly removed, but stacking buffs definitely are not. I've tested this countless times as earth main being hit by Mifune/Wind Main and it definitely does not removed the stacked defense.

Is it because stacks are counted as an Aura? Is this unintentional because it doesn't occur very often?