Earlier quoted context omitted.
I think it's more about the energy level needed to get over the learning curve. Like learning a new language, if you aren't really serious it isn't going to happen, and going at it slower makes it take disproportionately longer, making it disproportionately more likely you'll get frustrated and give up before you succeed at it. As for younger versus older, I'd say this is a screening process that filters young people…
This is why I think on-the-job training is important. I know there isn't much of an economic argument for a company to take on older candidates and teach them how to be a productive developer, but maybe subsidies would help? I don't know, I just don't think we can reasonably expect people to retrain on their own time... especially if they're dealing with financial stress already.
Many govt programs criticized in the article do support people through the training. It was more about people being encouraged to reskill into the wrong fields when it comes to programming (which I didn't agree with, by the way).
A "pull based" system where companies recruit people to train based on their needs does have benefits over letting people guess and run up debt on their own (the current system, which crashes and burns when people make bad predictions). The govt does this, e.g. where the military will pay for your education in return for service. But do we really want people deeply indebted to private employers? Otherwise they'd only be willing to risk training people a limited amount, since trained employees will subsequently only stay a limited duration on average. The is how it more or less already is.