Lots of good points in this thread, but yea, I'm still surprised by a 57:30. I'm more surprised by 4 people in 57:xx...
Wanjiru set the 58:33 in 2007, then Zersenay at 58:22 in 2010...then nothing for 9 years. It seemed as if the 58:22 was in fact underrated.
In that time since Zersenday set 58:22, the marathon world record was set 4 times to go from Haile's 2:03:59 down to 2:01:39, yet the half marathon stayed firm, even with a hotly contested WC every year (or is it every other?) and lots of big named races.
The "shoes" started to be a thing in like 2016, and while we've seen a lot of guys go fast, only one set a WR in them (2:01:39).
The one fellow that came out of nowhere and ran 58:12(?) was suspiscious, and rightly so. Then Kamworwor ran 58:01 and that seemed otherworldly, and he is a half champ and 2x XC so it was believable.
So yea, someone taking 30s out of Kam's record is pretty unbelievable, even if the scoring tables show it is in fact more in line now.