DD, The service load for a 6 pdr is 1.25 lbs for solid shot which would give you 1400-1500 fps. The question was which would kill more people solid shot or splinters? The senerio was pirate ships and their prey. Pirate ships and merchant ships did not have the same type of hulls as warships. Pirate ships and merchant ships were most likely armed with relatively light guns compared to warships. So what you saw was reasonably accurate, and their conclusion was reasonable up to a point. They concluded that you would most likely get killed by cannonballs (correct) and that you would have to be standing very close to the side of the ship to get hurt by splinters and that you wouldn't get killed by them, which may be correct when dealing with pirate ships. This senerio does not deal with warships that used heavier guns and thicker hulls which is probably where the "myth" came from. The record indicates that splinters did cause wounds, but the idea that more deaths would be caused by splinters than cannonballs does not make sense when you consider the energy of a cannonball to a splinter.
Side note, Shattering charges produced more damage to structures, and was achieved by reducing the powder charge. The lower velocity created more damage. This is may be why the mythbusters air cannon had such damaging effects.
Possible setup for a new show "myth" would be to construct an accurate representation of the side of a warship and use a large caliber cannonade. That would be really interesting.