Didn't read the article, but if it's the same stuff going around the net, then the terms they use are incorrect.
All phones are unlocked in HK, it's just when the iPhone5 rolled out, PCCW failed to meet the LTE standards set by Apple. They can still use the phone, but Internet access is just 3G.
There's a more complex answer. By meeting Apples LTE standards, mobile carriers have to start abandoning their 2G base of users, and there's less and less of them now. The company that owns PCCW still has a large base of 2G users and are either not willing to force them go to 3G or adapt to the frequency used by Apple.