If you have a cheap set of German knives ridiculously thick all around what difference does it make really, except your diamond hone won't last very long. Even DMT's have a problem here. The nickel typically use to bond them isn't very strong, and the harder the steel the easier they rip out. This is greatly exaggerated with a round hone because of the extra pressure exerted at the smaller point of contact.
I had a 1x3" fine diamond hone that I used for 25 years, but I only used it to finish sharpen a very thin and soft 9" stainless blade. Actually I went from a course (relatively speaking) India stone (an unnecessary step really but at the time I thought you were suppose to always start with a fresh edge), to the diamond, and finished on a soft Arkansas. I hadn't used it for a while when one day I pulled it out to see what I could do with a cheap ceramic parer I'd picked up. It tore out most of what was left in the hone just touching up the edge.
Atoma diamond hones are bonded with a different process and are much more durable than DMT's, and some pro sharpeners do use them for thinning, but never finishing, unless they're hacks.
If you want real fast cutting and great finish both then cubic boron nitride (CBN) is the way, but at this time it is only available in slurry and compound form for stropping and lapping, no one is making stones with it to my knowledge, and it does have a problem in that it reacts with certain metals which can quickly reduce its effectiveness, so you probably won't see it in whetstone form.