I posed that question to Garmin and a number of people who I thought would know.The Garmin Support team folks were not sure and had a variety of guesses. A few 'in the know' people I asked thought along the lines of my guess - that is, some sort of vibration or harmonic dampener from the rudder cables to the yaw servo. Not so technical, but a safety device.
Here's the response from a Garmin engineer >
Mike Huff
Field Service Engineer
Experimental Aviation Support
1200 E. 151st Street
Olathe, KS 66062, USA
Phone: +1.866-854-8433
The halo! That is so the rudder cables (A) cannot loop themselves over the bolts that attach the bridle cables (B):

__________________
Jeff Warren
Simpsonville, SC (@SC47 > 10nm NW Triple Tree)
1946 Bellanca Cruisair 14-13-2 (73 YRS OLD 8/15/19)
RV14A (N14ZT), Ser#140195
Start 10/11/14
Dues paid 12/1/19 (USArmy 2/67-2/70)
www.mykitlog.com/jeffw@sc47