Yes, I had a look at that. The issue is that setting an array for the system (config:system:set) is different from setting an array for an app (config:app:set). When using occ config:app:set one of the options is to specify an array as the type, and for the occ config:system:set you need to set the individual values for the array. The issue is still that I don’t know the syntax of the value parameter.
System level values can be set in the way described in the doc link @j-ed posted.
Though (I believe) you have highlighted a still outstanding doc need after server PR #41755 related to app level systems. It just happens it shouldn’t matter in your use case since that app you’re needing this for uses system level values.