When I did that (select both, Cmd-Shift-L), this app stopped seeing them as duplicates. What really needed to happen is for the Contacts app to Link the duplicates between the two accounts. This app wanted to “delete the duplicates”. In my use case, I keep duplicates of many contacts in a Gmail account I share with my partner. There was only one thing I let it do for me and otherwise used the analysis to guide my cleanup tasks, but only because it gave a little more information than the native app does and let me see things side by side more easily. For what the use I got it wasn’t worth the $5.
