Exactly. Most Documentaries get away with using what they use under fair use.
You almost couldn't criticize anyone using video without "fair use" kicking in...
...it is a balance of the interests between educating the public and exploitation of someone's copyright. Fair use wouldn't apply if they used the whole match or a large portion of the match but to show the winning shot and Serena lifting the trophy in the context of her life story seems to this entertainment attorney to be text book "fair use".
That said, there could still be a settlement but it would be cosmetic...USTA gets a couple thousand and the doc makers get official permission...it is always better to have official permission if you can get it...fair use is usually a fall back position.