The world is full of useless or impractical things that sell.
Ain't that the truth.
Any product for which you can find buyers is a valid one...
Hardly an example of effective resource utilisation - but in this commercial world, true enough.
I find this thing very stupid, but there are certainly other people who don't have the same goals/interests as me who will love it.
And quite likely they will have a gym membership - so they can keep fit.
As I see it, for Dave to have any basis for a debunk, there would need to be claims on battery life, pulling power, gradient negotiating capacity, turning circle and that sort of thing. You know, engineering stuff.
Also, I can't see the manufacturer or supplier offering a sample for a teardown.