Tire flat at tyre storage (tire dealers) Possibly rip off?

Today I had an appointment to change tyres (tire dealer/workshop) and I was told “when we got the wheels out was a mature flat and put a screw in it and “we recommend two tires otherwise the differential can break. All tires Run on flat 6mm profile. Has anyone here already experienced similar things? Is it possible to rip off some tire dealers to make more money?