So what? Is 10 some mental limit of names for most population? If I can memorize 8 I can handle 12 or 15, or neither. Making up sub-categories is such a typical bureaucrat's approach to problems.
Why should giant planets be in same category as normal ones? Why mixing ringed with non-ringed? Why mixing moonless with moon-enabled? Gas/liquid ones and solids? I could go on for a long time.
The definition of a Planet could be whatever we want. It could be "these named entities are planets, other things are not planets" if we wanted. That makes a hell of a lot more sense to me than anything else, because eventually we are going to find planets which really blur the boundaries we have currently. Until we observe the entire universe, any set of rules we come up with are going to appear to be wrong in some situations.
