I had Hybrid clipless/platforms on my fixed conversion for a bit. I had pretty much decided to switch to pure clipless because I never used the paltforms (I don't wear flippy floppies; at this point my regular everyday shoes and my summer sandals both have cleats on the bottom). Anyway, I was lazy and didn't get to changin g the pedals until I had a really nasty crash from a pedal strike. At least on mine, that platform side sticks down further than the bottom of any other pedal.
I don't imagine such pedals would be permitted at my track. YMMV.