If you want clients to be connected at Wifi 6, then you need to have Wifi6 capable Access Points as well as Wifi6 capable clients. 2702 is not Wifi6 supported, its 802.11ac Wave 1 (Wifi5) supported AP.
If you want to check from WLC whether the clients are connecting to AX capable radios
CatalystOS - show wireless client summary (look for the protocol column)
AireOS - show client summary (look for the protocol column)