Do you mean the Wi-Fi option in Settings? It doesn't have SSID priority, but it does have an "Avoid poor connections" option. If enabled, it only connects to Wi-Fi networks that have a strong connection.
Yea I couldn't find anything like that in the advanced WiFi settings so I figured as much. I'm using WiFi Connection Manager now. Allows you to prioritize SSIDs and appears to be working. I've got multiple APs/SSIDS going while I test my coverage/channel options and wanted an easier way to ensure that the SSID I want to test is the one I'm connected to without having to turn an AP/radio off or forget a network's settings or change the band.