"Having all necessary or normal parts, components, or steps; entire."I view that word in it's literal definition.
I see where you're coming from. But imagine having like a bowl of ice cream or something. At that point, you already have a complete dessert. Now let's say you add chocolate. Was the bowl of ice cream sans chocolate "incomplete?" It would be weird to argue that.
You're absolutely right about some games being marked as completed when they're definitely not. But "complete" does not always mean "no more updates."
Anyway, I'll let you have the last word on this if you want it. This is a pointless argument.