Before today, Illaoi could get 5 stacks of Dark Harvest for every spirit that she killed. Killed as in, brought to 0 HP - If you run out of the range of the spirit or do enough damage to her that you get it back, she gets no stacks. Today this was patched out, but what wasn't fixed is that if you die at a distance from Illaoi, i.e to a Vessel-spawning tentacle that kills you, Illaoi does not get any stacks.
If you're going to nerf a champion's synergy with a keystone at least fix all of the inconsistencies. If you die to a Vessel spawn then I should get stacks for it.