I don't think that really proves anything, it's unsurprising that recumbent bicycles are represented less in the training data and so it's less able to produce

I don't think that really proves anything, it's unsurprising that recumbent bicycles are represented less in the training data and so it's less able to produce them. Try something that's roughly equally popular, like a Turkey riding a Scooter, or a Yak driving a Tractor.