My thought (giving them benefit of the doubt) was that perhaps they knew that somewhere in the vicinity of 28-45 had been looking recently, but not with per-min

My thought (giving them benefit of the doubt) was that perhaps they knew that somewhere in the vicinity of 28-45 had been looking recently, but not with per-minute confidence. So they fix that range and then randomly pick something from that range to display on each page load. But that is giving them a lot of benefit!