High tea belongs mainly in farming communities in my mind - you have the sandwiches and cakes, but also a carved joint such as ham, pickles, bread, something like pork pies, an altogether more substantial meal, suitable for farm hands after their work. Afternoon tea, on the other hand, is more gentile, and can be quite a spread, but smaller bites, ladylike proportions, not huge plates of meats, breads, pies, etc.

I suspect Hong Kong would tend towards afternoon tea more than farmers high tea.