I’ve had a WM-8H for 10 years now. 9 years were on my Boomer 30 with 28hp engine, 22.5hp pto. It chips nearly everything I’ve put through it. It can handle anything that isn’t firewood, though I may have to slow down the infeed or pause it a few times on a big log to let it recover.
That said, I got a 47hp LS last year, with 38 hp pto. It is much faster.
I wouldn’t be afraid of using the 8H on a 23hp tractor if it’s all you have. It won’t be as fast as a high HP tractor, but it will still work.
Only complaint on it is I wish I could use more than 20% of the hydraulic flow adjustment. It’s 0 to 100% speed in just a small portion of the travel.