It is normal that the two zones water on different days--different soil types.
The observation was that the Watering History showed this watering as a "manual" watering and the Schedule updates show that the Iro was off line an hour before the Flex schedule was to run. I have no indications that my internet was down at the time. I did not institute a manual run, and the run time corresponds to when the Flex schedule should have run. The moisture graphs do, as you note, have it right.
I noticed another interesting event in the Schedule updates when going back to look at this.
"Last Monday at 3:17 AM
Flex schedule Grass Flex processing skipped due to freeze delay"
I kind of doubt that the temperature got that low--this is August in Southern California! The Flex schedule ran the next available day. The stations site only goes back 3 days, so I can't tell if the weather service hiccoughed.