It's one of the most popular TNG storylines and not everyone will spend the money on season sets. More frugal and less hardcore fans can easily pick up some HD TNG goodness. So, to answer your question: yes, there is a point.
I don't count it as a double dip, but if you are a completist, it least the bonus features are nice. And I love the documentaries on these Blus so far.
If these single releases sell well enough, you may see other sets ("Best of" Themed sets like "Klingons", "Borg, "Time Travel") as was done with the DVDs after the season sets came out of various TV shows.
If the prices are reasonable (like the Target sale on Season 3 and TBOBW set was) I will pick up these "mini-movie" edits. They are also good for loaning out to friends!
But I don't consider them "essential"