Refreshing a lesson gives me vocab I didn't learn the first time
Nothing else to say, really - when I went to review a lesson, a lot of vocabulary came up that it hadn't taught me the first time.
If you have gone through the lesson only once, there will be a fair number of sentences you were not exposed to. Redoing the lesson a few times will expose you to some more sentences. And revision of the skill a times may throw up a few more new sentences. That's how it's always been.