More or less, you're right. Thing is, most marines don't know anything about the common slang used by everyday players like Hydro, Marshals, Engineering and such so you're pretty much forced to use directions everytime you give squads orders like "Move East to Nexus and then get to Medical that's NW of Nexus". Also, you can mostly ignore this if all the squads have experienced SLs with good rep who know what they're doing. As for the marines that don't want to listen, let them be, nothing can be done about it.
TL;DR Don't announce "QUEEN ON DELTA SL!!1!" and use the damned directions