Agreed. The very fact that there is a 40 post debate about the OP's "fly straight out" (FSO) seems like pretty good evidence there is not a widely accepted meaning. Fly runway heading = zero debate. Maybe someone could misinterpret the murky "FSO" instruction to mean "FSO to your destination"! (that would seem impossibly stupid, until a pilot came along and did it) Query; ask for clarification.