The computer has short and long term fuel trim (tweaks to the original fuel mapping that are unique to your car).
It also should have knock sensors that often are used to optimize timing curves that would be more likely to be affected by octane. It doesn't "know" it's different gas, just that it is more resistant to detonation.
I'd guess that it's as said, just slightly harder to light off.
May also be a warning to do a fuel filter if it's got a bunch of miles on it.