@Michael Insufficient testing is not the expression I'd choose. There was recently a recall from Babboe, but it's interesting to see that on their website, they don't mention the standard they are testing against, only the certification body (which is a red flag for me). If looking at the specs, they only mention the rider max weight and the cargo max weight, but not the combined max weight.
@Michael Yep, I don't deny that. The point I wanted to make is there's a difference between insufficient and inadequate. In terms of communication, I think that mentioning a standard (if you consider the mainstream one to inadequate) is also more important than the certification body (a bit like the manufacturers of speed-bikes helmets, that like to refer to a non-mandatory Dutch standard rather than the EN one).
@Michael sounds good, but isn't it (a) the other way round? We use gears to bring down pedal force to comfortable values. (b) it doesn't really matter if you do weight lifting with 3, 4, or 5 kg. All the forces are still so small that strengthening effects are minuscule compared to cardio or muscle efficiency effects.