The Short Story...If you have installed the trailer wiring you already have the logic circuit to make the stop lights do dual purpose and flash...just like your trailer.
Cut the wire that powers the left brake light...near the light, tape the end that supplies the power, attach a new piece of wire to the light end, thread it down to the single wire that supplies both turn and brake to the left trailer light (Yellow) and splice it in. Repeat for the right side (green).
Now your brake lights should do dual purpose just like is required on a trailer.
Disclaimer: Do at your own risk. I think you either “get” what I am saying or you don’t. I am sure someone will try this and let you know that it works. Our Telluride will not be here for a few months yet and I have not decided if I will be installing the hitch and wiring. Note the hitch and wiring is now available at many other sources other than the Kia dealer and at much better pricing.
The only thing that may be questionable is the smarts of the vehicle may not like that the brake wire is not connected to a light. However because it is attached somewhere in the line to the the trailer harness, it should be ok. Worst case would be you have to connect a small bulb or led and stuff it behind the panel.