Frank, In looking at it again, and "playing" with it, I concur that it’s set up correctly,
but it was a little out of adjustment.
I ran it for a little bit 1/2 hour before I took the video, and it idled
a lot slower. Determined this morning that the throttle butterfly was not shutting
all the way, and suppose that one of the trunions slipped a little.
I now have it so it works smooth, and goes fully open and closed. Have
not run it yet, as it was raining. Peeks of sun coming out, so maybe later today.
Anyway, from what you said about the "intent" of the setup, etc., and
from me playing with it, I believe it’s working correctly now, and note that……

At Full spark advance on the mag plate, there is full throttle control, from
idle to fast on the twist grip. As the spark advance is reduced, the setup
limits the throttle opening, which make sense.

Interesting answers so far on the trivia question!
Thanks.

quote Garry in Tampa:

the electric start early 1930 motors which used a RPM controller in the starter/generator to adjust the timing. 😎

Garry, are you describing some kind of mechanical governor with
weights as the RPM controller, attached to the starter / generator?
Interesting!

Finally got around to re-testing the Sea Bee after
tinkering around with the throttle and mag linkage this morning.
The throttle shuts all the way now, and it idles down
real nice. After the video, I had it idling down quite
a bit slower. Hope to get it on the lake next weekend
to give it a whirl.
I took the rewind off to inspect as it "rattled" yesterday.
Motor sounds a like nicer now!
The rope plate has some play where you can rock it some.
Will have to tear it apart and see if it’s curable.

https://youtu.be/m2t7MnWJlDs