Witches and demons transform and their lives flow faster than they actually do

When the witch presses the maximum health value low enough, the demon voice changing skill shows a loss of 0.1 life per second, but in reality, it is about 1 life per second, with a difference of 10 times between the former and the latter.

PoE 2 Bug Reports:
https://www.pathofexile.com/forum/view-forum/2214

This was a patch changed early into the EA. The minimum life lost is 1 life per second. I don't have the exact wording from the patch right now, but I believe it was to avoid abuse cases with CI and offsetting with flat life regen.