I've experienced a couple of dunno-if-it's a bug using the chainsaw....
the first is that the chainsaw don't harvest the rubber tree leaves (even if it does it with other mod's one so it might be intended)
the second is that harvesting leaves with the chainsaw have still the chance of dropping saplings/apple If I can remember right doing so with the shears don't do it (if intended or can't helped cause base code editing double profit )
I had even a bug with the drill not fast gathering soulsand but that seems to have been fixed some versions ago