Smaller bikes are a more wide spread issue in the bike industry than the biggest sizes. It's a shame you can't get what you want but it's not just limited to the taller end of the size curve.
Amflow didn't even make any size small or smaller bikes. I'm sure you could at least source an XXL if you pay enough, even if that does mean a pre-owned one. No such possibilities if you want a smaller one. Bike fitters tend to say you can make a smaller bike bigger but you can't make a too big a bike fit.
We're bound to see more companies bring out bikes using the Avinox system that will cater to other sizes. Or even alternative competitive motor systems in different bikes in a wider range of sizes. Tech is just going to keep getting better and better, something is bound to come out that you had wished you waited for whatever you end up getting.