I personally would be hard pressed to call anything under 400cc a Maxi scooter. No doubt that 300cc is a big step up from a 150cc but not quite a maxi. A real maxi to me would be 500cc and higher with 600cc and up being the more genuine maxi.
But as said, as long as it's fun who cares what the lable says. If you had a partner that was 30 years your senior and she/he was still fun to ride, who cares, it's your ride.