Why does Clemency get interrupted? And why does Sword/Shield Oath reset combo?

[Freyyy]

I'm a little embarrassed to admit I don't know exactly what Oaths cost, but they're in the neighborhood of ~1k MP at 60 if I recall correctly. I *think* it's about 1,200, but I don't recall for certain.

Pretty sure it's 884. Grit is 1326.