And so the TOS Enterprise can easily fit into three classifications at the same time.
- Star Ship class (primary mission profile)
- Heavy Cruiser class (type of vessel)
- Constitution-class (ship's configuration)
I have no problem with that.
In fact we know that all three of those apply, because various canon sources have said so. The numerous 'starship' references in TOS, ditto for 'Heavy Cruiser', and (if I may mention TNG here) Picard flat-out says that the 1701 is Constitution
class in "The Naked Now" and "Relics".
So they can be, and in fact are, all true.