That’s not true. The track log, at the bottom of the page, shows it ascended from 37k ft to 39k ft at about 5:10 PM PST and held until about 6:00 PM when it descended into Ontario. It does not give times in EST anywhere on the page. Are you sure you are looking at Nov. 8th and not today’s flight?
As a side note, aircraft ascend as they burn off fuel because their engines work more efficiently at higher altitudes (depending on the winds). Higher is better, even for relatively short periods of time.