I have been watching the default Beechcraft setting with engines running and the parking brake on for the last 15 minutes - has not moved an inch.
I have only observed the "creep" on one or two aircraft I have downloaded over the past few years - most do not exhibit this behavoir - and never I have I seen it in any of the default aircraft.
So I feel safe in saying it is NOT a FS2004 issue as the OP would have us believe.