We have seen these animations and stance before with:

Gaius: Used gunblade - had this stance
Fordola: Used gunblade - had this stance
Nero: Used gunblade - had this stance

You can see the same animations being used in both the Gaius 2.0 solo fight(https://youtu.be/lA8hy5WWxvY at 4:15) and again with Fordola solo fight(https://youtu.be/zbMgju95vqw at 8:25) but you can tell with them both doing the lazy version of the RDM sword swipe attack. I think it wasnt as noticeable before because both Gaius and Fordola had flashier attacks during the battle whereas Nero is right beside us doing simple attacks.