Why do I get onto:explicit statements when querying onto:implicit statements in GraphDB?

Question

On querying statements from onto:implicit in GraphDB 10.0.0 using SPARQL I also get onto:explicit results. Here is an example:

select * from <http://www.ontotext.com/implicit> where { 
    ?s ?p ?o .
}

Gives me all statements with context onto:implicit AND onto:explicit. Only when I add a MINUS command it returns only the onto:implicit statements.

select * from <http://www.ontotext.com/implicit> where { 
    ?s ?p ?o .
    minus{
        graph <http://www.ontotext.com/explicit> {
            ?s ?p ?o .
        }
    }
}

Why is that? Fyi: If I use from named <http://www.ontotext.com/implicit> not even the version with MINUS works.