X% Damage taken from Mana before Life inconsistent (Xbox)

Last few deaths I rewatched.

1600 HP, 3500 Mana, and 50% of damage taken from Mana before life

So if I go from 1600 to 0 I should see an equivalent drop in Mana but the mana doesn't move.

I could understand if the stat said "physical/elemental damage before life" since there are recoup nodes that make this distinction but this says flat damage and seems to be inconsistent

I could also understand if it was Regen in the same frame but mine isn't that high, about 800 and it doesn't even tick