Trailer rear brake lights

Hi all,

Well, the time is getting closer and closer to when we can actually take our Tab out for its maiden voyage. We've been delayed about 2 months for various logistics and parts issues but that's a story for a different time ... today we finally got our tow hitch receiver installed on our TV!

We got home and connected the 7-pin and all seemed to be working great. Tested again with the Curt Echo brake controller this time. The first shot there was some quirky behavior and only the right side would illuminate. After disconnecting and reconnecting the Curt, all seemed to be well.

However, 1 thing stood out to me and my wife - only the 2 larger red circular lights would respond to our inputs. The smaller outermost lights did not illuminate regardless of turn signal, headlight, brake application, or hazards.

I'd like to ask:

a) is that expected?
b) if so, what is the function of the 2 smaller rear red lights?