Backblading was always seen as the unskilled operators method of trying to smooth out washboard, that he'd made, trying to level going forwards.
Anytime I did back-blading when I was being taught at age 16, I'd get hollered at, and told not to do it - it was the sign of an incompetent operator.
Then there's the likely damage caused to cutting edge nuts and bolt threads when you hit something such as a rock when dragging the blade backwards in float. A badly worn cutting edge is most susceptible to this problem.
That's damage guaranteed to make you curse, if you're the one who has to change the edge when it's worn out. Secondly, there's the chance of damage to a new cutting edge if you hit a rock whilst back-blading.
The cutting edge has support when travelling forward, it has no support when travelling backwards.
In the old days before better quality cutting edges such as the boron alloy steel we have today, it wasn't unusual for you to be able to break a chunk out of the cutting edge if you whacked a rock whilst back-blading, particularly if you were travelling in 2nd or 3rd reverse.
Having said all that, it
is necessary to do back-blading occasionally, when you need a totally smooth surface, not chopped up by grousers. It just pays to ensure that there's no rocks in the surface you're back-blading.