As you can see from the photo below, it definitely leaves marks in the wood which is to be expected given this is a very coarse grit of 24.
As a knock-off, I'd rate this product an 8 out of 10 with 10 being the highest. I've seen some videos of the "Holey Galahad" in action, and this one doesn't come close to the same amount of sawdust being made, but, for the work I do, this is good enough.
Plus, the price is right at a modest $9.99. I can go through a lot of these before I get to the price of a "Holy Galahad" at $79 each. That makes this product even more attractive from my perspective. Might take a bit more to "finish" grind the surface (essentially two more steps using router planer and belt sander, and another step for finish sanding) because of the relatively deep gouges made by the grinding wheel, but not all THAT much.
I even used this grinding wheel to take down a surface on a pedestal I'm working on that'll ultimately wind up being a television stand (looks kind of off kilter in the photo, but is actually pretty level all things considered):
This grinding wheel is an in-store purchase only. If you'd like more specs on it, go to the Harbor Freight page here.
It doesn't say if it's to be used with wood or not, but I did it anyway, and I'll say I'm satisfied so far. Still don't know how long it'll last, but hopefully long enough to make it cost effective. Labor intensity I'd be rating at a 5 simply because I'm old!