This is correct and intentionally implemented this way.
Therefore Googlebot receives an extra http-header X-Robots-Tag: noindex for pages which really should not be indexed. See:
https://github.com/discourse/discourse/commit/758e1608626ce78566dd39004a4a6251d3bbfc60
For your own domains you may use Google Search Console → Inspect URL
Then try to add a user-profile url to index – e.g. https://www.example.com/u/jacob
