In an other thread MantisSifuFW says:

Master Luo Guangyu, on the other hand, began to blend Meihua, Qixing and Guangbang forming his own Tanglang. Hong Kong Tanglang is not Qixing or Meihua, it is a mixture. Today some HK styles call themselves Qixing but this is not either historically or technically accurate.
very interesting! It makes sence in some way. Where do you get this infos from? What makes you believe this?

It would be a logic explaination for the differences between Mainland and HK 7*....