I read somewhere, true or not, that Wireless Android Auto requires 5Ghz Wifi, and most earlier cars (mine included) have only 2.5Ghz, so they don't support it. The reason for 5Ghz had something to do with that being the only band where a mobile access point was permitted or something.

Could be misremembering, or could be total hogwash.

Note that one/both of those two after market adapters both claim to support it on 2.4Ghz as well as 5Ghz.