Thanks. The air pressure is about 85% of sea level pressure at that altitude. Maybe that's enough to get some data about how the engine responds, but it's nothing like a real launch, and I think it's borderline fair for Tim Dodd to say these that "none have ever really flown" in the context of orbital rocketry.
I think Tim didn't know about that launch, that's why decided to add to the discussion. Not having data is not the same as not having flown; not only the flight has symbolic value but also, I'm sure, the flight serves as an incentive to all participants, especially students. 1.3 km altitude for a liquid fuel rocket is a very real launch, believe me, for amateur participants.
In the context of the video, which focused on technical details, I personally don't think the symbolic or incentive value is relevant. I'm glad you raised the point though.
