It's not really a requirement on cross cutting, there its the fence and its placement in relation to the gullets of the teeth.
In rip it stops the kerf closing up as tensions are released on the timber, which can make it move,twist or close together. If the timber closes together on the back of the blade the up motion of it grips the board and flings it up and out back towards you.
Actually with longer boards its as much a problem as theres more chance the timber will move as tension is released from it.
In cross cutting its best to use a sub fence that is the correct width you want to cut, but leaves the actual fence well back. As the timber needs only to be sized to that sub fence its really only acting as a stop. Actually that sounds rather convoluted. Hopefully someone else will happen along to explain it better