Jeff,
The heat shielding, in the form of a ceramic blanket/reflective foil, doesn't weigh very much and will insulate servos and leads from the tailpipe heat. I'ver witnessed several turbine powered jets crash due to failed servos and burnt leads and a lack of any shielding. Maybe this can be phrased in form of a recommendation rather than a rule.
I was expecting some form of acknowledgement upon submitting my pulse jet declaration to AMA early this year.
Rgds,
Art ARRO