5EAT cold 4th -> 5th shift problem

This morning while leaving for work, my car (06 LGT 5EAT) would not shift from 4th to 5th at the usual 25mph mark. This time the "up" arrow from 4th to 5th did not show up until I hit around 45mph. I've never seen this happen before, but this is the first winter where I don't do a lot of highway driving.

 

My morning routine:

Turn the car on (25F this morning), turn on all the butt warmers/heaters/defrosters/etc, pull out of the parking lot onto a 45mph road (it's early enough that there's nobody on the road, so I *gingerly* hit the throttle, getting my car from 0-50mph in about a minute. I always use the sport-shift when the car is cold because I can't stand the hard shifts (I know it revs the engine higher to warm the engine up quicker). So when I hit 25mph, I got ready to knock the trans into 5th, but the light never came on until I was at about 45mph. No more problems the rest of the morning (5.5 mile commute).

 

Maintenance:

I've got 70k on the clock, and changed rear diff fluid at around 65k and trans & front diff fluids at 67k. Transmission fluid is the Subaru ATF fluid. I'm currently at 5500miles on my OCI, M1 Ow40... I checked the oil this weekend and it definitely ready to be changed, but was nowhere near "overdone". I don't drive my car too aggressively and I'm stock in terms of everything.

 

Any thoughts?

This is normal operation. It's an emissions thing. The 5eat TCU will not upshift to 5th in auto mode nor allow an upshift to 5th in sport mode when operating temp is too cold.