Stone saw vs. Hand saw

Ok, so to put it bluntly does the hand saw have a lower rate of giving coffin planks ?
I chopped about 5 trees using the stone saw and got 2, since then i have cut maybe 15~20 using the hand saw, and still nothing.
Bug? Intended? RNG?
I chopped about 5 trees using the stone saw and got 2, since then i have cut maybe 15~20 using the hand saw, and still nothing.
Bug? Intended? RNG?