I've been through HKG airport a lot, and am very aware that if your carry-on is oversized or even close to being so, you need to get a carry-on tag when you check in or your bag(s) will be sized at the entrance to security/passport control and they will not let you carry it in if it doesn't fit in the sizer.

But I've never noticed a scale. I'm quite sure they are only looking for oversized bags (why HKIA should care when each airline has its own carry-on limits that are up to them to enforce, not airport authority thugs).

Regarding EVA actually weighing a carry-on, I have only heard of one acquaintance who said EVA check-in counter made him weigh his carry-on in EWR. In all my years checking in at LAX, SFO, SEA, TPE, HKG, I have never had EVA require me to weigh my carry-on.