Not a big deal, but in 10 years of being a Plat I've not encountered this: Original flight scheduled to depart at 3:40pm. At 11:45AM, I started getting voicemails from NWA with delay information, starting at 30 min, then at 12:00PM, they made it 45, then at 3PM they moved it to an 80-min delay. (FYI, now it's 115--the first 2 delays were due to late inbound AC, now they're ATC delays).
Got to check-in at 3:15pm, about 75 minutes before then-5pm departure, and Ticket Agent said the flight had been restricted aleady. He called to confirm, and yes he was unable to do anything. He printed me some kind of voucher to get me past TSA, and I went to the gate--they'd already printed up BPs with other names on them, so they ripped one up and gave me back my original seat in F, 2D. So, no drama--it's a reasonably short flight, so I'm not chuffed if I end up in coach (I do like the 1,000 mile Plat UG Guarantee!). But anyone else who had checked in "late"--but still an hour before the new time--probably lost their upgrade.

So, those in the know: Why would they restrict a flight so early? I realize the original check-in deadline was 3:10PM, but why would they bother to send updates if they still needed me to check in by the original cutoff?
Thanks!