Just a thought that came to me last night at about 4 am, while up for different reasons.
People who can y/b/m, both co and ua, are being encouraged to book co right now, as they can (often) instantly upgrade. OTOH, people on non-y/b/m fares are being steered to ua, both for a higher chance of ELR(especially with the new sale policy), and the (seeming) better chance of an actual EUA. Not sure how this changes for people doing international Y, but I'd lean towards UA metal due to the e+, especially if row 32 is booked. I wouldn't be surprised if CO/UA is really doing some deep analysis on people's patterns with that, to get metrics and generate policies going forward. I know my leisure travel would be on UA metal, vs business travel on CO. I tend to be a last minute B+ fare purchase, often TPAC, so I have to be a profitable customer.
Thoughts?