possibly as a side-effect of the "clean handlebars" styling. Some British bikes around the late 1930s had internal throttles, wiring inside the handlebars, speedos inset into the tanks and tank-top panels of various sorts. These sometimes included choke cable-pulls.
The Amal carbs of the time had cable-operated chokes and the coil ignition systems which were coming into use typically had automatic or fixed advance timing. So did the Bendix carbs of the 60s and 70s.
Given that the shovelhead acquired a pull-cable choke through the dash centre bolt, long after everyone else had stopped using that styling, could this be an early provision for that feature?
Shoot, a man could have a good weekend in Dallas with all that stuff...