Out of 8 games suggested, 3 had been already sold back to Amazon through their trade-in program. The fourth game that I highlighted was purchased from Amazon under the same account that received the email. Two of the highlighted games had been originally purchased through the same account that received the email.
A "civilian" would go "well, how the hell are they supposed to account for THAT" but this being Amazon, I am sure that it is possible for them to add purchased and traded items as exclusion criteria to the queries used to mine for our emails. I am 49% sure that everyone received the same list of games, but these being so popular maybe it would had been a better idea to refine the criteria a bit more.