Waiting for proof from UAL that a crew was being re-positioned, and not just a commuting crew that were being accommodated by their co-workers.
If you're hanging your assumptions on that, I predict you'll be disappointed. I've displaced pax many times as a DH crew member. I've been commuting for 17 of my 19 years in the airlines (not UA) have never once been accommodated over a paying pax when not on company assignment. Not once. The thought of it happening to cover 4 Pax is ludicrious. The contract airline has aircraft that are crewed by 4, so 4 pax being removed is consistent with a DH assignment. If you were airline, you'd know how improbable your conspiracy theory is. First, there's no love lost between gate agents and crews and second, the agent would be the one to have to deal with 4 denied boarding school and have to justify it down line during audits.
You can cling to the idea or accept that your idea isn't a starter.