Isn't the main argument against employing older developers that they won't have that level of focus and determination? Pointing to an statistical anomaly and suggesting that older people can be that focused is easily countered with an argument that, while that's true, it's far more likely that a younger person will have the traits you're looking for, so you should employ them instead.
A rare example of a hyper-focused older person[1] isn't a reason to hire older people. Hiring is about filling a position with someone capable of doing what's necessary. It's not about finding someone exceptional. You want to get someone in and get them up to speed as fast as you can in order to move on to doing things that drive your business forwards. To that end, older, experienced people are very often better than younger people because they've already proven they can do the job.
"won't have that level of focus and determination"
More like they won't have that level of focus and determination for a poorly run project - so it's not that they can't it's more that they won't see the benefits to them of that level of dedication.
On the other hand, however, physical decline is more rapid than mental decline and we're talking about a middle-aged man able to play with the best pro athletes in the world -- seems as clear an example of any of experience trumping raw youthful energy. Peyton Manning's last season or two seems like another good example.
Well it was not meant to be countered, it is meant to be inspirational. Some say a statistical anomaly, others would say a hero.
I do agree with your expanded point, by the way. Would just add that the veterans can bring that and more; the right person can inspire & impact the performance of everybody on the team.
Perhaps it's anecdotal too but I work in mainframes (myself being 38) with both younger and older colleagues and the ones that are older seem to be far more focused and determined (perhaps "work ethic" is the most apt word for it) than the younger ones. I can even feel it myself looking back.
A rare example of a hyper-focused older person[1] isn't a reason to hire older people. Hiring is about filling a position with someone capable of doing what's necessary. It's not about finding someone exceptional. You want to get someone in and get them up to speed as fast as you can in order to move on to doing things that drive your business forwards. To that end, older, experienced people are very often better than younger people because they've already proven they can do the job.
[1] 44 isn't old.