In my opinion, having liability Insurance doesn't convey quality in the product, but it does mean a smart business person has their butt covered. I suppose a lot of resellers start on a shoestring, but once they get successful, they realize they have assets to protect.
Insurance is a business decision. I might carry a $2M umbrella. Doesn't make me a safer driver.
The Consumer Product Safety Commission has definitions on bicycle safety. Big box shops like Target, Walmart, etc, are not going to sell products that can't meet CPSC. Sure, the tests are modest. A hand brake bike has to stop within 15 feet with a 150 lb rider at 10 mph.
If someone puts a $200 kilowatt motor on a $200 WMT bike and hits 30 mph, well that's a case of "hold my beer and watch this".
I'd have to see a BTN before I could judge, but if Jangles recommends his bikes, then I'll accept his opinion.