Interesting. I guess this means the 23.05 Release Notes notes are a little misleading since the example would set the MACs to only what is listed instead of adding.
I’ll have to test mkOptionDefault a bit more. i think if you had another but regular MACs = [ "AA" ] assignment (e.g. in separate files that are recursively merged) then it would silently override both the module default and mkOptionDefault instead of throwing due to conflicting definitions. (For now I’m just adding my own check via config.asserts.)