Function allows_aggregations 

pub fn allows_aggregations(
    names: &NameOverrides,
    schema: &str,
    table: &str,
    role: &str,
) -> bool

Whether a role may ask for aggregates over a table.

Separate from reading its rows because counting rows you cannot see is a way of seeing them, and Hasura keeps the two apart for that reason. A role the document says nothing about is not reached here: it has no table.