Yes, normally no occupied car ahead of a pusher. No rear pushers on passenger trains. On most railroads the pushers would be cut in ahead of wood framed cabooses. When steel cabooses came into being then the big railroads where willing to push on the very rear behind the cabooses.
However, I recall hearing about how the New York Central used pushers on their passenger trains on a grade at Albany, New York. They pushed closed coupler knuckle to closed knuckle when they got to the top of the grade the pusher shut down and the passenger train kept going.
B Norden