MFSimulation.load() Method Looks for DIS Package in Model Path Rather Than Path Specified in model.nam File

[mrush-usgs]

When I try to load a simulation using:
sim = MFSimulation.load(sim_ws=model_pth)

flopy looks for the DIS package in model_pth, rather than the relative path that is specified in my model.nam file:
dis6 ..\external_files\model.dis dis

I am using the develop branch. When I install the master branch, I get a similar error, but with the TDIS package instead. For the time being, I have commented out lines 1583 - 1584 in mfpackage.py:

        # if model_or_sim.type.lower() == "model":
        #    filename = os.path.split(filename)[-1]