Only partially correct; yes, some extremely Left or Right people are Independents, but most are either Democrat or Republican which is why most moderates have left their parties to become Independents. I was a Republican for over three decades but finally became fed up with the extreme direction the party was moving.
To paraphrase Reagan, "I didn't leave the Republican party. The Republican party left me".
As the link below demonstrates, Party members are more partisan and dislike their opposites more strongly than Independents even though Independents lean toward one party or the other.
5 facts about America’s political independents