Good point. However, sellers are motivated to sell for a wide variety of reasons. So a seller's valuation may change depending on circumstances -- if a seller needs cash quickly, for example. A seller in dire need of cash may accept the $3,850 offer for RnR.com, and BD is probably well aware of that. Otherwise, why wouldn't the seller just hold onto the domain and wait for an end-user offer to come along?
But you're right -- BD would likely suspect that the seller knows something about domain valuation after submitting multiple quality domains.