@Kav, every AP always allows basic roaming if set to the same existing SSID and same encryption method / same encryption key. This is a basic feature of the 802.11 WiFi standard which exists since the standard was created for the first time.
Only restriction is that you can't use »fast roaming« (aka »seamless roaming«) offered by Omada EAPs since this requires the use special protocols (802.11k/v) and an AP controller which needs to manage all APs.
Note, that if a WiFi-6 device did associate with the AX6000 WLAN and the WiFi signal is still good, it might not necessarily switch to a WiFi-5 EAP-Outdoor even if you're standing nearby this EAP. The roaming decision is always made by the client device and there are several methods in use by different devices.