Not sure if this is expected behavior. I was seeing dupes of the same transaction being added into the Spending Plan. The pending credit card transaction has cleared but the corresponding pending item had not yet been removed. It was showing me as overspent in a few categories which felt incorrect.
I went in and manually excluded these pending transactions from Spending plan and it adjusted correctly. (I then noticed watchlist was also showing dupes so I excluded them in reports).
Suggestion: It would be more helpful to be able to hide pending transactions with one click once you know transactions are cleared. ie exclude from all projections