A possibility is that UA has enough marketing intelligence that NickRivas is a potentially valuable/wooable passenger.

I had something similar(ish) happen with AA a couple years ago--The same year I spent ~$45k (in PQD measures) with UA I "had" to fly AA in F to BDA because the *A option was something like 8x the cost and required an overnight in YYZ -- and since the majority of the trip wouldn't even be on UA metal and I had long stopped worrying about 1K requalification I figured AA vs AC didn't make a difference.

A few months later (and completely unsolicited) AA gifted me some level of status + a bunch of PP-equivalents to "try flying AA some more" -- unfortunately my schedule (and UA club access rules) for the status period didn't really make spreading my flying around practical so much of that was wasted and -- but I did make use of them on a CLE-DFW-CLE round trip just before the MD80s were put out to pasture (needless to say I found neither the airport or airplane hard product particularly greener grass) -- and had AA been a few month earlier or later with the offer they may have won at least some of my business over a longer period of time.

It would totally make sense to "surprise and delight" a passenger you know is doing a lot of flying with someone else to try to encourage them to do more of that flying with you.