Right. One episode."Amok Time" is not early installment. Second season.
The rest were still early and them figuring Spock out. I feel the point is still valid.
And Spock wasn't "unable to smile." Once the character was cemented, he just normally didn't. He was embracing his Vulcan side, this was a key point of his character - even his mother made an issue out of it.
If it did smile, it was an extreme situation (Kirk alive and his career saved and whatever in that episode) or some kind of manipulation (again, once he was figured out). This is why it's such a big deal when he does. As he was fond of blabbing every week - and is in his starfleet file seen in The Menagerie - is IS half human.