First off, there is no way to know if Bob Iger actually did fully ride 100% of the RotR.
But in reality, the opening date for RotR at Disneyland was decided by the Marketing folks.
They wanted to get past the VERY popular Christmas Season and its possible Sold Out days in late December, early January.
The choice was Martin Luther King, Jr. Holiday weekend, partially to get some guaranteed large crowds, plus to allow ads to run for the first couple of weeks in January, in a time frame that other parks tend to not heavily advertise.
So when the ride geeks said we can be ready to open in December, but not 100% sure due to Cal DOSH, the decision was made to wait until January.
And sine WDW doesn't have the Christmas impact Anaheim does, Orlando decides to open when the ride geeks say they are ready....