To be fair, when I'm 40 I can't imagine still wanting to work 12+ hours a day. I'd like to see my family. This alone makes me feel like the age bias is caused more by people realizing the work won't work with their goals. The article itself seems a bit off since it doesn't deal with data so much as a single anecdote.
When I'm 40, I hope I have my life structured so I can work 12+ hours a day -- enough resources to automate or outsource the tasks I don't enjoy, no need to commute, etc.