Shavronne's Satchel - not working as intended?

It does not recover any energy shield when i use a life flask with it, is it bugged or am i not understanding the wording correctly?

Wording is the same as in "Supreme Decadence" in pt.1, so, i guess, it works in same fashion - you only recover ES when there is some life to recover. Using flask on full life does nothing.

Does that mean it would only recover as much es as it does hp? That would make sense why it doesn't seem to do anything?
Since i am using it with demon form i'm constantly degening hp that means i'm pretty much nvr on full life and can pop hp flasks anytime, but getting no es recovery from it with the belt equipped.