A GPU doesn't get you a double upgrade to GF. There is also no rule that a g/a has to move a BF pax to GF and then accommodate a Y pax one section north.
If there is no-one standing by for GF from BF the non-rev gets the front of the plane. That is why they call GF, "Employee Class"! UAL sets these rules and not the g/a. Nope, nothing fishy here!