Session target wordcount gets influenced by docs that are not counted

It’s not the first I’m seeing this, and I’m not sure whether it is me or a bug.

Windows 8.1 / 10 (happens also under Wine, which is set to W10)
Scrivener v.3.1.4.1

Session target is set to allow negatives and does not include text written anywhere in the project. Project target is set to count current compile group only and to only count documents set to be included in compile. No deadlines are set.

So. I have status labels assigned to all documents. Some statuses are set to be excluded from compile, so they don’t get included in the total wordcount. These documents usually hold scene summaries.

When I want to start writing actual text, I open such document, select all and cut everything (moving it to an external editor for reference). The number on the total wordcount bar doesn’t change. Then I change the document’s status label to something that gets included in the total wordcount. The number on the total wordcount bar still doesn’t change, however the number of words that have been in that doc prior to its inclusion gets deducted from the current session wordcount.

It seems weird to me to deduct words that have never been counted in the first place. Is that normal? Is that maybe something about my setup?