@jprzpam Thanks for the additional information. The team has informed me that, unfortunately, for the moment, graphQuery is not available for Slice Machine. We have an open issue in the tracker. Whenever we have news or updates about this topic, we'll update this thread:
In the meantime, I recommend that you do a separate query for the home-page that all its Slices. I understand that this process defeats the purpose of graphQuery with Content relationship fields, but it is the best workaround for the moment.