We don't know the cause of the difference in price, but we're comparing two basic economy tickets here so if there's any fare difference, United should at least clarify to the user why...

United and other airlines are running ads [0] on how users can book w/ confidence and get free changes so IMO, it's just irresponsible to have things like this slip through the cracks-- intentional or not.

Overall, United has been consistently being anti-user with their policies related to coronavirus. For example, making users wait 12 months to get a cash refund [1] if your flight is delayed by them. Not a great look.

[0]: https://twitter.com/tejasmanohar/status/1239332916070473728

[1]: https://www.dansdeals.com/points-travel/airlines/united/unit...