SBG8300 MAC Filtering Not Working

I setup WiFi MAC filtering on my SBG8300 when I got it a year ago. I manually added my device MAC’s and set to Allow. From what I understand, it should only allow those listed devices to connect to my WiFi with WiFi password and no other devices should be able to connect even with correct password. I discovered that devices not on the allow list are able to connect with the password. I tried setting the list to Deny, save settings, my device MAC’s in the now Deny list could still connect to Wifi. I have had the guest networks disabled since I got it. So the MAC filtering feature seems to be not working at all no matter how its set. Is there another setting somewhere that could be conflicting? I would rather not do factory reset, takes long time to setup this router and can’t save config.