If you leave a gap, it can snag wheels and rollers, and it will chew the heck out of rubber tires.
I built some hi-railer modules with Gargraves and Ross track years ago. I filed that *@$^%%#*$ nub down on EVERY track pin. What a tedious pain in the tuchus! The idea of the nub is good but IMO they are too big as they come out of the stamping die.
If you leave the bump on the pin and push the hollow rail over it, you *could* introduce a slight hump at the joint, or a "pinch point" in the gauge. If the pinch point is in a curve, or a loco's wheels are already gauged a little too wide, then it will hesitate at that spot which ruins the realism. Bottom line I recommend you file the pins down at least a little so they JUST grab the inside of the rail. My $.02.