Does UA have a different concept of "Sort: Arrival Time" than is commonly understood?

Trying to book a return from a Vegas tradeshow to get home as early as possible while also hopefully avoiding either a redeye or a 5am departure. "I know!" I said to myself, rather than sorting by departure time [which works as expected], I'll sort by Arrival Time.

The appropriate arrival time sort order is, as far as I can tell United has determined:
8:27 AM (off to a good start)
10:41 PM (what?)
2:36 PM (ok, not as bad as 10 PM)
9:45 AM (huh, seems like this should have been right after the 8am option)
6:53 PM
9:54 AM
11:45 PM
6:10 AM
8:18 PM
4:54 PM
11:14 AM
11:14 AM (even oddly this option and the one immediately prior depart from LAS at 12:59 AM, have an hour and 21 minutes at IAH and arrive at 11:14 AM, but the "Lowest Economy (Refundable)" first one is $631 for T class, and the 2nd is $893 for H class)
7:03 PM
11:44 PM
10:08 AM
9:54 AM
6:30 PM
12:01 AM (+1)
11:41 AM
etc.