Allen had some back luck in playoffs

always playing on the road

and also so few teams in playoffs in the 1960s

He may have had some "McVay-like" success with more of an open field in PO.
But those were the rules of the game and his regular season success
trading picks for players worked for him.

It just that it was a tough field back then, Vikings, Dallas, and other teams
that stopped his Rams and Redskins.