I don't know if these nonsensical reviews are written by ChatGPT or something, but they are clear and utter lies.
I'm watching this series currently and I can DEFINITELY say that the footage seen is brand new. I have watched almost EVERY SINGLE Attenborough show available (even the rare ones and I even have them on Blu-ray), so I know this for sure. A few scenes might be similar to what was already done before (the star-nosed mole for example), but even those are shot in a beautiful new way. Besides, some scenes feature animal behaviour never seen before. Have you ever seen false killer whales sharing food? Or a close-up of a baby sperm whale suckling? Or a pod of orcas tricking and literally kidnapping a baby humpback? And this is just one episode. These scenes are unique even by BBC standards. And no, the narration is not reused. (C'mon... What's with this reviewer who said that??)
My only slight problem is that the series features too much well-known species and very few rare ones. If I stay in the 'Water' episode, I would have loved to see beaked whales, or pygmy sperm whales, or similar, less-known species. Yes, they are hard to film, but not harder than some behaviours seen in the series. So a few rarities would have been nice too.
I give Mammals a 10/10, even though I would have given a 9/10 if the previous reviews wouldn't have triggered my sense of justice. :)