Hi Brian,I've got terrible news, I tested this with the Shopify GraphQL app and since found the error in my ways - this is still not available to us, only Shopify and Apps made by Shopify. For the record I was using 2020-04.
Sorry for getting everyones hopes up.
Makes no sense to not have it enabled...
I just tried it with a Private App using the API version 2020-07 and apparently the read_publications and write_publications scopes are still not available.
Yeah - you can get it enabled by staff, but it's only for Plus shops. For us lowly Shopify plan users, we're out of luck.