The stack object is used on abilities that happens on dests other than player, as can be seen on this example where Rising Anger is only applied on boss, but the announce would say "3 stacks of Rising Anger on you":

Since the localized string uses "... on you", this object would only make sense to be applied on player stacks, not other stacks (like boss stacks):
https://github.com/DeadlyBossMods/DBM-Unified/blob/f7f36c41e3e95371b9da60f0dbcd6e1eae5082c9/DBM-Core/localization.en.lua#L398

My proposal is to have a different object for these cases.