If anyone goes into researching the edit history of the Wikipedia article quoted above, you'll find that the quoted sentence was written by someone named HkCaGu.
There is no "conflict". Yes, there is a US CBP pre-clearance for eligibility for entry into the States (since admission to Guam does not guarantee admission to the States), but a passport is not "required" to establish that eligibility.
Two important points to note: If you fly from GUM-US through any foreign point (Japan or Island Hopper), you must have a passport. If you fly GUM-HNL, you must check in and get to the gate before specific pre-clearance cut-off times. Your boarding pass gets processed not when you enter the jet bridge but when you are admitted to the pre-clearance waiting area--they'll offload your bags if you don't show up in time.
Unlike SJU, there is no agricultural check since Guam is completely outside US customs jurisdiction. Arriving at HNL you go through a complete customs check with a higher US-territory allowance for purchases.
And BTW, Continental Micronesia allows bag checks on the evening before your early morning flights. They just hold your BP for pickup at a special counter the next morning.