John Allen made some updates to the SB Tire Sizing Systems page about a week ago and BMX sizes like OS20 and 18" x 1.0" (ISO 400, the bane of many a race parent) are now included. The kid-race fractional sizes (451 and 520) now have improved descriptions. While 457 (the 22" of this thread) now gets a proper BMX mention (and several additional street/park/freestyle widths), wires were crossed: the page states that it's also a racing cruiser size. I sent a follow up email to correct this a few days ago. Fingers crossed.

If you want to get in touch with John Allen, you can get his email address within a few clicks starting with his name in the revised-by line at the top of the article. (Emailing the general contact address on the SB website didn't get me anywhere, BTW.)