Fascinating discussion. I've worked for one of the largest and top law firms in America. Its policy (as of a few years ago) was Y everywhere except for red-eyes or flights of 5 or 6 hours or more (I can't remember which), in which case J was allowed. This made for some funny choices by some of the lawyers who weren't hustling home to families or whatever. They'd add a layover to book J and just work from an airport lounge instead of hurrying home on the nonstop in Y to go work from their apartment instead.

I think there also were some routes where some flights were over the mark and others were not, depending on airline or time or year or something, and people would change their plans to book the flight that showed at 2 minutes over the J eligibility marker rather than 3 minutes under it. The travel service contracted by the firm offered zero flexibility whatsoever, leading to absurd results like these.