I just did HKG-GUM-KIX on Tuesday. UA would have sold me HKG-GUM-HNL with a 50 minute connection time, and I would have made that flight. After exiting TSA and walking to my gate, there was a huge line of people going to HNL preclearance. I could have stepped right in. They were boarding Group 2 into the waiting room (there is a very odd double boarding of 200) as I passed.
This is with TSA Pre. The lines were as long as I have ever seen them in Guam, but certainly shorter than 10 minutes and likely closer to 5.