From my experience it's not unusual, some do and some don't. Don't forget the idle is usually a bit quicker if you've only just started it and the engine is cold.
It seems to be the same with lots of different scooters. My Silverwing does it sometimes if not warmed up.
My PCX will also do it.
I think that, so long as you can easily stop it with your hand, then you're ok and it's fine.