If the TL-WR902AC works at client mode, it can be only connected via wired connection.
It won't provide wireless connection any more. In that case, there is no internet access even you can connect to that default tplink SSID.
Therefore, there is no much difference even you can connect to it because you can't access it.

That's not what I am experiencing. Here are the repro steps:

1. Set selector switch on chassis to Client mode
2. Factory reset using reset button
3. Connect to TP-Link_* default network from laptop
4. Navigate to 192.168.0.1 in browser
5. Go through Quick Setup for Client mode, as described in manual, connecting to WPA2-PSK protected 2.4GHz network
6. Router will reboot
7. Observe that both TP-Link_* network are still visible, with the 5GHz network being unprotected (no password at all)
8. Connect to TP-Link_* 5GHz network from laptop
9. Observe you can ping hosts on the LAN and even go to the internet, all from the 5GHz unprotected network

I have reproduced this several times, from two different laptops.

@brockamer I confirm the issue.

 

You can shut the 5G by going to Wireless 5GHz > Extended Network and uncheck Enable.