Are garages required to buy higher quality catalytic converters than private citizens?

Recently left my 1996 Ford Ranger at the garage. They had it for a few days because they had a difficult time locating the new converter. I found one that would fit on a local auto parts store web site. They said that one was fine for me to buy if I installed it myself, but they had recently been audited specifically for catalytic converter sales. They needed an exact replacement… Significantly more money. I do live in New York where bureaucrats are pricks. Were they telling me the truth?

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