From my knowledge PR makes a technical stop in Guam only if needed (heavy) (ie most the time) and sometimes also in HNL and notifies you prior to take off. Sometimes it can go direct but rarely.
Return flights MNL to LAX are direct no stop over.
You are not booking LAX to GUM... you are just stopping for Fuel... You're not getting out unless you are technical and have to layover.
(flew this one time, LAX to MNL to BKK and return)