Delta showed upgrade option to one traveler but not the other on identical booking

My wife and I purchased the exact same round trip flight on Delta at the same time. Same base fare, same cabin, same fare conditions. We were sitting next to each other looking at the booking screens together.

Today, I was offered an upgrade using miles and was able to upgrade. My wife was not shown the same option at the exact same time.

There is no visible difference between the two bookings. Same flight, same fare, same timing. From a customer perspective, showing one traveler an option while withholding it from another on an identical booking feels like discrimination.

Has anyone experienced this before?