Hmm, looks like by "hardware hackathons" he really means "making software for more resource-constrained platforms". Nothing wrong with that, but I don't think that's a right name for it. Also adding some soldering to it won't make much difference.

When my daughter was 4 y.o. she went to robotics classes where they assembled a small LEGO robot and made software for it using environment like Scratch. That's a good activity, but my point is that doing some assembly doesn't put the task into entirely different category of difficulty

If 3D printing were a bit faster, a BYO robot hackathon could have some really cool outputs for different weight/size classes etc.