When driving in Sport Mode, I notice the RPMs are quite high when decelerating on the highway and generally increase when I hit the brakes. Is this normal?

Its normal.

just like Krylon said… it’s normal

but to go more in depth, it’s normal because sport mode is designed to keep your TLX in the high rpms for quick acceleration. If you’re in sport mode it assumes the driver wants the rpms high to stay in the “power”.

i may be wrong but this is how I view sport and sport plus modes and why they change the whole atmosphere of the engine from calm to sports car-like

Yup, normal as mentioned above. What’s happening is the vehicle is selecting the next lower gear when you’re braking in anticipation that you’ll want to be at an ideal power band level; assuming you’re going to take a turn, the engine would be at a higher rev range for once you’re ready to floor the gas pedal. Enjoy!

The 10-speed auto tranny is doing match-rev downshifts during deceleration. So when you hit the gas to accelerate again, the tranny will be in the optimum gear for instant acceleration response.

Yes, the computer keeps the enginer RPM higher to ensure the turbo is spinning at a faster speed. These two in combination lead to a very responsive engine vs regular mode. Eco mode tries to minimize RPM and reduce fuel consumption.

Yep, it's what I thought the transmission computer was trying to do. It's just that the old TLX sport mode was quite different. But then it wasn't a Type S

I always like driving in Sport mode :-)

Thanks everyone for the replies.