In my opinion using the same supplier for two different products doesn’t fully satisfy the dual source requirement. While yes it does provide an alternative product in case the primary one isn’t available for whatever reason, but the problem for me is that it isn’t from a different supplier. There could be situations where the supplier is closed or has shut down, so your primary and secondary sources are both unavailable. If it were a different company then regardless of what is going with Company 1, Company 2 should be available. Using a secondary company does entail having them qualified for use with whatever process the company uses, such as signing a NDA or what not, but it should ensure a reliable second source.