I don't think it's necessarily a bug. I think it's just as interesting and fun, or moreso, that it's based on the starting dominion, since as KO said, it makes that decision more meaningful and lasting.
"Plopp" is a great term.
What I still wonder though, is whether a plopp will ever vanish in a friendly-dominion province that is at maximum dominion, or not? That is, if a nation has a plopp originating in a province surrounded by full-strength friendly dominion provinces, will it always work its way out to try to have an effect on the frontier of the dominion somewhere? Or is it likely to have no effect, dying somewhere in a maximum-friendly-dominion province? (That's all one question I was trying to make clear - forlot if it's confusing!)
PvK