This has been my experience with similar tools (mostly openvas / greenbone) and companies peddling vulnerability tests for compliance purposes. There doesn't seem to be a lot of "functional scanning" in this space, like you're talking about.
So I agree the false positives are a pain in networks with patched systems but this also seems to be standard behavior.
So I agree the false positives are a pain in networks with patched systems but this also seems to be standard behavior.