Thanks for the reply Jerrod.
I tested this today with a couple of AP-365's running as Instant and managed by Central. I had two AP-365's, one connected to a switch with internet connectivity, the other AP-365 was connected to a switch to provide power only. The mesh point AP wasn't configured with Eth 0 bridging as downlink bridging was not needed and the mesh link never came up.
Extended SSID was disabled and normally this is all that is needed to get this running but but not today. I will do some more testing then raise to TAC if needed.