Incorrect. In the oldest terms, yes, a cuckold is a man whose woman has cheated on him and is typically raising the other man's kid. The term is derived from a bird that does the same. In terms of fetishes, which is the relevant context to pornography and pornographic games, in a cuckolding fetish the cuck gets off on his woman cheating on him.
In Netorare, the woman cheats on the main (typically she is stolen by someone with more to offer) character, very much against their will. Typically the reader is meant to empathize with his misery. Why the fuck that appeals to so many I still don't understand, and probably never will.
Netorare is commonly enjoyed by cucks or people with a cuck fetish, but it is not, in itself, a cuck fetish.
You would think so, wouldn't you? But considering how much Netorare is on this site, compared to how much Netori, and the support the former drums up, I don't imagine that would be the case here.