IMO, the expansion tank is just that - an overflow reservoir that provides coolant when needed (low temp) and is a place for coolant to go (hot temp). It is not really an indication of the proper coolant level in your car. Of course, an empty tank indicates a problem.
You could have low expansion tank level (cold temp), add fluid, and then find it eventually goes back to reading "low". That's only because you actually put in a little too much, and so it only leaks out again until it reads just like before.
It's better to be a bit OCD on oil, trans, diff and brake fluid levels.
Overfilled, even if hot, but nothing to worry about. Maybe they're compensating for trapped air that hasn't burped out yet? Also, shouldn't they have updated to the latest yelllow-green spec or do they maintain the original spec?