How big is your Wössner China Moon? I grew a few from small (not super small) to medium sized seedling to blooming size. Overall, I don't find them expecially slow compared to other paph seedlings I've tried.
So far, I have bloomed two plants which came from the same batch. One has proved to be a really good grower&bloomer. It is special since it is my first and best so far. It bloomed for the first time in 2017. Then, it has bloomed a few times since. If you search under this hybrid name, you should be able to find a couple of my older thread on this.
The sibling plant bloomed around the same time, but it has never bloomed again since. It has two near mature growths at the moment. So, there is a stark difference between these two.
Now, I have two single growth seedling in sheath, which I'm very excited about. I have sold a few large seedlings last year, but kept three to myself. Two of those are now in sheath. The other one is far behind these two, but I kept it because the leaves are extra pretty compared to many other plants of this cross I've seen.
I have quite a few hangianum primary hybrids, and I would say Liberty Taiwan( x micranthum) has been the slowest for me.
Good luck with yours!