Life reducing Mana Flask not working properly with Birthright Buckle (POE2)

(For POE2)

When using my mana flask that removes 15% of life on use it isn't proc'ing the life lose when I get the Birthright Buckle Wide Belt instant recover proc at low mana. The life lose works correctly when using my mana flask at a higher mana amounts that are too high to activate the instant recover from the buckle. This is a trivial bug in the grand scheme of things, but is annoying for my low life build when I'm trying to stay in the low life range. I imagine the belt is ignoring the mana flask modifier's and just refilling the entire amount when it procs and for the majority of players it doesn't matter what the flasks modifiers are it's just counterproductive for my build. The belt is using charges correctly by the way.