To reproduce:

1. Post some things at a Flow board in some namespace - e.g. "Wikipedia talk"
2. Go to Special:Contributions/Your name
3. Set the namespace filter to "(article)" and tick "Invert selection"
4. Click "Search"

Expected result: You are shown all edits outside of mainspace and also Flow posts.

Actual result: You are shown all edits outside of mainspace but not Flow posts.

However, if you set the namespace filter to the namespace you made the Flow posts in, and do not invert it, you will get the expected result: edits in that namespace and also Flow posts.