I think you've hit it. Each test runs as a separate tsqlt.run call rather than a larger call with all results.

At the end of the day, I really only worry about failing tests. That's the concern, but if you have multiples, really you have to run them one by one to get the results for analysis. Kind of a pain.

Open UserVoice (or vote) suggestions, as I'd like to see more work on SQL Test done to improve it