Sorry don't understand- what resources would such passenger movement hog?

I've been through it in HKG (IRROPs) and TPE (checked baggage security issue). In both times airline staff have to authorise and security has to verify identity and log.

Free shower at arrival level pre HK immigration or the transit checkpoints

Pretty sure this is bring your own everything... even a towel.

Vending machine - tap your Octopus "doot"!

VIsitors aren't expected to have Octopus, before exiting arrivals level.

The vending machines accept V/M, but, not all the time https://medium.com/@haomiao/the-best...d-1600aeae134a

HKG could do with better arrival facilities
And I hope this is remedied in new T2
But the lack thereof doesn't mean we should make exceptions the norm/BAU/entitled behaviour
It will be the same argument that European/North American/western world baggage handling is bad, so we should be allowed to bring whatever we want on selfish/passive aggressive-behaviour:

https://www.flyertalk.com/forum/brit...y-madness.html
https://www.flyertalk.com/forum/brit...ambles-19.html

We had them- octopus for tourists app on iPhone. Load with your credit card. No physical card necessary.

How much revenue do transit pax bring to HKIA? Likewise to CX?

Many routes wouldn't be viable at all without transit pax, and transit pax allow strong routes to operate at greater frequency, but the home market is obviously a primary focus (HK isn't Doha).

I am arriving at gate 31 - how far is the Cathay transfer desk from it please?

https://cimg9.ibsrv.net/gimg/www.fly...45b9315b52.jpg
There's also Transfer Desk E2, which is at a similar location as E1 but on the left/south side instead of right/north as in the above graphic

If connecting in HKG, does one have to go through immigration, or not necessary if we have a boarding pass for another international destination?

If have BP, no immigration

Only if you need to collect checked bags and recheck them for the new flight. Otherwise you just need to pass through a transit security check between the arrivals and departures level.

We did not during our trip last Feb. We had a long layover, so stored our carryon luggage (for a fee) and took the train into the city for a few hours, then took the tram up to Victoria Peak.