I just called. Theoretically "it's all good" as business class will get you in. We'll see about that.

*However* I neglected the fact that my flight out of SEA leaves at 1:30 am. Might throw a wrench into the same-day flight requirements. Did not have that issue with Oneworld (they honored outbound lounge access even though that last AA flight I mentioned left at 12:30 am. Hoping it is the same with CO.