Yeah, not sure if author knows, they certainly don't share if they understand this or not, but these things aren't available because the some governments say those frequencies are illegal to use. Turkey for example has multiple frequencies under 5Ghz WiFi that is banned, hence consumer don't get to use 5Ghz WiFi. If you change that, you're breaking the law and you might get a visit, depending on how hardcore they are about the rules. Tend to be pretty strict and swift payback when it comes to using frequencies you shouldn't, as they're used for other stuff and easily seen when other traffic appears.