All of the bells actually...
Probably indicates poor long term maintenance by the previous owner. The PO only cared enough to keep the car moving. Tires should be replaced as a set, not one at a time. Different makes and models of tires replaced at different times means they are all worn differently, have different overall diameters probably, different traction levels, etc. Not good, tell the dealer you at least want a new set of tires that are all the same. Kind of makes you wonder about the history of the car and what else has been neglected.:surprise: Check the suspension, see if the shocks and struts are all the same and look under the car to see if any other parts have been replaced or if there is any other sign of damage or repair.
Tires get replaced one at a time when there are specific wear problems, like if there is an alignment issue. Or if a tire got shredded (it happens, but rarely), or if the car was in a minor accident and a tire was compromised.
I'd ask for the results of a 4-wheel alignment from them.
I hate non-matching tires on a car. I would take it as a bad sign.