This incident looks pretty supicious to me.
The Chileans know better. And, the Secret Service
wasn't on there toes here. They should have been in
the room before the President arrived. All the security
people should have been aquainted with each other
before the event to prevent mix-ups like this.
(If it was a "mix-up".)
Your assesment is the most astute that I have yet read, however... in the end, it was handled and it was handled with authority and genuine leadership that the DU types cannot blow off as a planned photo op.
TT