Thing is, the PMDG 737’s (and many other third party planes like the CRJ) don’t interact with the world map, so the ingame ATC has nothing to go on.
If you’re using simbrief to plan, export your simbrief plan to both MSFS’s .PLN format, and the 737 formats.
Load the .PLN in the world map, then load in the plane, and load up your flightplan in there.
With a simbrief flightplan loaded in the world map, the ATC will be much better behaved, and will generally get the TOD correctly.