Why should the fact that you come from a programming world mean that the idea of a stack is foreign to you? Surely the idea of pushd/popd is quite obvious to a programmer? (I.e: I dont give a crap where i am now, take me back to the last place i was....)
It means that there's no association between the term "pushd" (which he saw as an abbreviation of "pushed") and changing directories. Nothing to do with foreignness of stacks.