Seems fairly likely that the purser was first through customs and approached the counter. If the sky priority agent was free then she was probably called over. They seem to do this all the time with folks in the econ line if things are slow. At that point I don't think anyone stands aside if a sky priority person shows up in line.

Now the statement about the NRSA's having priority in a premium line is laughable. What they did or didn't do to get the OP on the earlier flight IDK...