Hmm... A named pipe may be temporary in the same sense that a regular file (or a network connection or anything else that provides a "handle" on data) can be temporary, i.e. it may be set up by a script to facilitate some sort of processing, and then deleted before the script exits. ItIt would then be a "temporary (named) pipe".
A named pipe is a file, and so one could argue that the temporary named pipe (which is indeed temporary) is a temporary file.
However, in when people refer to a "file" then almost always refer to a "regular file" (i.e. a document of some description), and a named pipe is not a regular file.
A pipe in the shell, set up with | to provide a stream of data from one utility to another, is temporary in the sense that the shell will deallocate any resources related to it when it has been used and is no longer needed.
In the end, pipes (both named and not named) and regular files have different applications, and it should be clear when a regular file is used to store temporary data, and when a named pipe is used to pass data to another process.
