The supposed categories breakdown whenever one actually studies existing and historic operations. PRR not only operated EMUs on both mainline and suburban branch routes, but also operated de facto commuter trains from west of Philly through to NYC--marketing both 44 ride punch and unlimited monthly passes. Both classes of tix were good on any PRR train between NYC sand PHL other than a few of the premier (Broadway Limited, Pittsburgher--both all Pullman) and Florida trains. And FWIW, RDCs on the B&O in MD continued until the state bought newer equipment hauling riders into DC and Baltimore. In the Chicago area, one branch of the FRA compliant Metra Electric Division operates entirely within the city linking several neighborhoods to each other as well as to the CBD. Entirely high platform, this service pioneered electronic fare gates in the 1960s.

SMART is a compromise, useful for some of us. As to heavy or light,or commuter, it is FFRA compliant IINM, but then so is the PATH subway system in NJ and NYC. With temporal separation, it could operate with"lighter" cars,and if the Marinites weren't soodious NIMBYs become a faster system with short er headways. As to not reaching the City, the GGB was engineered to carry NWP cars on alower deck., or when the Richmond SR Bridge gets replaced (hopefully before it falls over), it could take SMART to either a transfer to BART, or a junction w/the Capitol Corridor.