that's a pretty broad statement
I know all standard leagues award fumble recoveries as TD's to any player who scores them, offense or defense.
and every custom league I've ever been in does the same, whether I'm setting it up or someone else
I don't understand why, if you start Frank Gore, and he scores a TD whether it is rushing, receiving, recovering a fumble, blocking a punt or returning a kick...why he shouldn't get those 6 points?
That truly would make no sense.