I "played around" at playing the harmonica for years. It was just five years ago that I got serious, bought some harp instructons books and learned about the bending ability of the harp. It took me 10 months before I got my first bend, and then only on a very tight harp. My Big River's would not bend for me until I gave them the micropore treatment.
As for Asian harps and overblows, I also learned about overblows 5 years ago. Tried on Special 20's, Marine Bands, Lee Osker's, Big Rivers's and cheap Chinese harps: With and without micropore and without and without closing the reed gaps. Could not get a reed to crack on any of them. Not an overblow in the boxful.
Then last September my wife bought me a Suzuki Overdrive. I got my first overblow a month later. Easy on the 6 blow, but hard or impossible on the other holes. Last winter that sweet wife of mine got me four Suzuki valved M-350s: From low F to D. Figuritively speaking I was blown away. With ease I was able to get overblows in every hole on each of those four harps.
Seems as in the story, "Animal Farm": Some Asian harmonicas are more equal than others.