Alright, now I'm just getting curious
3 flights on this day are now showing 0 inventory in Y, but 6+ in J (with a bunch of Z/P inventory, which is what 1-way tickets are pricing into) and 2 more have just a single seat in Y (though if trying to book a 1-way, it doesn't actually offer the full-fare Y but instead offers up the P fare).
Update: My flight is down to 5 in J, but the rest are still 7+