This was definitely a thing just back in the 2000s. You had guys like melo, tmac, Paul pierce, wade, Dwight ect all decline in this age range or way before. People always mentioned lebron still being so good when he was 33. At first that seemed like an anomaly. Now, you have guys like curry, kd, kawhi, dame, lebron still(lol) jimmy butler, all still being in their prime at 33+. Is it an advancement in technology and medicine? Something else?
I can tell you that in the last ten years our understanding of recovery has moved forward by a lot. Just look at myofascial release for instance. That is now common practice among athletes of all levels while ten years ago it was a very niche branch of knowledge.