I almost always scuff every bat I get nowadays. I think that scuffing doesn't really take much performance away from bats at all, if any! The problem is that it does add half an ounce to the weight roughly, although this is hardly noticeable. I think that the pros do highly outweigh the cons, as it's much easier to maintain, without the need to oil and sand after every couple of uses, and there is noticeably less cracking as well.
I think bats from before anti-scuff sheets were pressed harder, and possibly had a higher moisture content, so didn't break as easily! Also, I find that the heavier the bat, the less prone it is to damage!
Knock it in first then.
Grains do not open up.
The surface gets harder creates a veneer a natural laminate.
Knock it in first then scuff it makes bats last longer.
I'm not too sure about this, as I tend to scuff first then knock in. I'll only knock in a natural faced bat after oiling, which softens the surface of the wood, while if you scuff it, it maintains a slightly harder surface. May very well work better though, and worth trying! I do oil the bat before I put on a scuff-sheet at times anyways if the bat looks in need of a drink! I think that scuff-sheets were made to hold the bat surface together for longer, so that they peak slightly later, but last longer as well. Grains opening up is a sign that a bat is at the best, but I think some bats are at their best even before the grains have opened!