I encountered the same issue on sentry.io. The Github repository is connected, the release contains commits and changed files information, the issues are attached to releases automatically, but suspect commits and assignee are never appearing in the issues.
I run into the same problem using the API. The official documentation is a little vague here. In one examples from Sentry documentation version is set to git commit hash in another to two digit version number. The example also states: it is assumed: source maps are uploaded, which I cannot do as I’m testing it with a simple python project. Source maps cannot be a requirement for suspected commits to work, or can it be? Finalizing realease thorugh API is not documented: I guess by setting th dateReleased… What happens when I deploy “unfinalized” release, will it be finalized automatically?