Yes yes I think we all agree.
It seems likely its fuel, but having a spark tester on hand will help verify that the next time it happens.
Even knowing its fuel, need to determine if its too much liquid fuel into the intake manifold, or whether too much is vaporizing (either in the line or in the carb).
Since we know it runs cold, he won't be able to investigate all this until it happens, or at least is hot enough it might show symptoms upon investigation.
The business about measuring timing is to have baseline information. Whomever set this up had enough of a clue that it runs and drives. But if not enough advanced it could be a contributor to the coolant running around 210 with only a short drive on a moderate day.