Not to justify them, but I'd want to bet on that most of those sellers don't even have a console cable.
They might just clean the dust, power it on holding reset for 30s, plug a cable on port 1 and another on any other ports and see if the device got a link UP and maybe a DHCP address.
And to be fair, reselling a bunch of used enterprise gear, of a ton of different vendors, with different console cable, different GUI and CLI, and know about all the messages that it spews out during boot... they'd be consultants, not sellers.
Most of the times (for me anyway), it does matter more how a seller react to a bad item, that receiving a bad item in itself... take for granted that $hit happens, now what? If the seller accepts to exchange or refund, I'd not be throwing rocks at him.