Audio Units Preference missing garageband 11 - Mojave 10.14.6

Under Preferences > Audio/Midi I see no option to enable Audio Units

This is what I should see:

This is what I do see - the option is missing:

System Details:

Garageband 11 version 6.0.5

Mojave 10.14.6

Ultimately I am trying to use a plugin, but I can't get the plugin to show up under my instruments without enabling this option from what I understand