To refer to the Netherlands as Holland or to call a Nederlander (someone from the Netherlands) a Hollander is akin to calling the USA "New York" or referring to an American as a Gringo. The Dutch consider it a derogatory term.
You are absolutely right. OP got confused because it is called "a constituent country within the Kingdom of the Netherlands". However, Sint Maarten is not a sovereign country and while they are autonomous on many internal affairs that doesn't make them independent. The term "country" usually refers to sovereign nations, however if one really wants to call Sint Maarten a country it would have to be "overseas country and territory" (OCT) as this is Sint Maarten's official status.
i read them. i got it too, but i just think it doesnt make that much sense to count the french territories to france but not the consituent countries of the kingdom of the netherlands to the netherlands.
If there'd be a name for me that I wouldn't like, I certainly wouldn't put up a website with exactly that name.