The HKIA website / app is as poor as HKIA is good!

I don't have a good answer for you, except to say that I have successfully transited the 62+ gate transit area a few months back, and I've walked by that transit area 3-4x in the last month (I seem to get "lucky" arrival gates of high 60s with some regularity), and it has always been open as I walked by in the last month. So good news! I can't say precisely when, butI haven't had any early am arrivals in the last few months, meaning I saw it open sometime between like midday and early evening.

It's worth pointing out, my observations lately (open) stands in contrast to the observations I had a year and two ago, when it was frequently closed. I also used to see all the other smaller ones closed to, like the mid 40s transit, and the one around the high 20s/early 30s (I can never remember precisely, but it's down the spine between the big two transit areas). However, I do not know the logic to it. I just presumed that HKIA was/is chronically low on staff, and air travellers hadn't fully recovered to pre-COVID levels, so they rationalized it. And now that we're getting back there things are finally returning 100%.

Fyi, we had a thread precisely for what you're asking, but it got moved from here prior to us getting a CX-specific moderator here (thanks to cxwaterboy for finally filling a role we were lacking for a few years!). This was it: Smaller HKIA Transit Points: Do They Ever Open (Esp near Pier?) I started that thread over a year ago and at that time I was noticing the small transit areas were regularly closed. I thought it was a mistake to move it out of the CX forum here, but now that we have this thread, it's redundant anyway.