Background: 2012 Honda Civic EX, 5-speed automatic, with no mods except a non-stock tire (ran over a large bolt). I keep it maintained per the manufacturer's manual and always see the Honda dealership that sold it to me new for maintenance. 20k miles.
Sometimes when I am going down an incline at about 65 mph and I need to brake a moderate amount (decelerating about 3 - 4 mph per second), my engine will rev up significantly. For example, if my cruising RPM at 65 mph is about 2100 RPM, it'll kick up to 2500 - 2800 RPM when braking, and only back down to about 1500 RPM once I either step on the gas again, or reach a very low speed (under 20 mph).
What is going on? Is the car shifting into a very low gear in anticipation of stopping very fast? I usually brake just enough to keep from running into the car ahead of me, and although the brake pedal isn't nearly fully depressed (like I said a "moderate" braking), I rarely have to bring the car to a full stop when I'm in this situation.
It seems fuel-inefficient to run the engine at 2500 - 3000 RPM for a good 15 or 20 seconds when I'm actually asking the car to decelerate. In other automatic cars I've owned (much older; 1997 and 2002), the engine's RPMs just gradually decline the slower you go. Neither my Civic nor my older cars use a continuously variable transmission. I am unaccustomed to this behavior and am looking to see if it is abnormal or something that this car just does because that's the way it's designed.
Update: Here some other people appear to be having the same problem.
For the record, I always drive with the "Econ" button ON and am applying steady brake pressure, not "pumping". It may be "Grade Logic" as one of the posters on that forum put it.