This is a common misconception and is in fact incorrect. I just wanted to clarify this in case someone is searching for info. Even if the AP is using Mesh as its uplink, you can still use the same radio for client access.
Believe it halves the theoretical bandwidth. A reason to avoid having it enabled unless you really need it. A wired AP can theoretcially provide a possible 300Mbs to it's clients whereas a meshed one only 150Mbs (please correct me if I'm wrong someone)!
Reduces WLANs per WLAN group from 8 to 6.
Reduces max possible VLANS from 256 to 192
To remove Mesh also requires ZD reset to default, in other words back to square one.
Problematic if you thought it was a good idea to enable it but didn't really need it. You can disable it on the APs but it will always remain enabled on the ZD until a default reset.