From my experience teaching older people when I was younger, and myself no longer being 20 anymore, the challenge is figuring out which assumptions to question.
Let's say I'm reading a math proof, and don't really understand a statement. If I pretend I understand it well enough and keep going it might make sense, or maybe I'll get further lost. I feel like I had a better sense both of how not to get bogged down, and when to slow down when I was younger.
The property of neoteny - the retention of juvenile features in adults is one of the things that humans are particular noted for, and learning is one of them. So we could well still be evolving the ability to learn later in life.
The other unknowable here is environment. It is a lot easier to learn things via the internet than it was even 10 years ago, and it is also a lot more important to keep learning in many jobs. So the really interesting experiment will be to take today´s 70 year olds, who had to be content with evening classes if they could find the time to learn new skills, and compare with today´s 20 year olds, in 50 years time.
In my peer group at least, the difference between those who never opened a book after they left school (a sad, but surprisingly large number of people even with university educations), and those who kept reading, is huge - which also supports the findings.
edit again - i'm a little slow today.. you're right, it might just be an accidental side-effect, sure.