Web Admin Radius Auth on Peplink Balance

We have a Peplink Balance 710 currently running on FW version 5.2.2.
We recently have enabled Radius authentication for web Admins. That works fine. However, in contrary to the description for Radius auth, the local admin account still works.
Shouldn’t that be disabled as long as the Radius server is reachabel?

is there a reason you are running five year old firmware?