That's a fairly common outcome if the delay is over 2 hours and there's no way to improve on it (here because the inbound into PHX is where it is). So there is a general "sorry but we're going to be late", which seems largely automated. And then a second message - presumably after talking to the ground handlers - that identifies a later baggage drop time. You are best to check-in online as soon as you can, if something is wrong with the ticket it's best to find that out on the old schedule.