Are you saying Wifi did not automatically connect while you had Ethernet connected, but that once you unplugged Ethernet Wifi did automatically connect ?
If so this is the expected behaviour. Even with SingleConnectedTechnology=false in /etc/connman.conf (a change we made recently) because Ethernet has higher priority than Wifi (PreferedTechnologies=ethernet,wifi in /etc/connman.conf) if you already have Ethernet plugged in (the higher priority device) it will not bother to auto connect the lower priority device.
You can still manually initiate a connection to wifi and they will both stay connected (until reboot) but it will only auto connect to wifi if Ethernet is unplugged. See the following connman documentation for an explanation: (Autoconnecting section)