I'd say it's the customer's responsibility to know what model/variation he has, and then Spyderco ships the parts requested. It's the customer's responsibility to get the model correct. Obviously, Spyderco cannot be responsible for determining what model/variation a customer owns. Same goes for counterfeits: Spyderco obviously can't be responsible for remotely determining whether someone's knife is a counterfeit or not. Why should they? The counterfeits are not under Spyderco warranty, nor is it Spyderco's responsibility to prevent people from procuring counterfeits, which would be impossible anyway.
The issue seems pretty cut and dried to me. Buyers request specific model/variation parts, pays for them, and Spyderco sends the parts requested.