For any young programmers: live within your means, invest the difference, become independent, and work on what you enjoy. It’s the best (work related) gift you can give yourself. Skip the self promotion politics unless you enjoy it.
The first part though is key - living within your means. It assumes you have means, and that it's possible to live within them.
The advice is good - whether you use it or not is up to you, and of no consequence to the advice giver. Whether you are in a position to take the advice or not is up to you.
For those who can though I can agree with it. Forgoing a new car now might mean retiring a year earlier. Financial freedom (aka retirement) means doing work on your terms, not beholden to your employer. It doesn't mean "not working".
Of course the best way to a better job, more pay, and a sooner retirement is indeed to "sell yourself" making both yourself and your work more valuable.
Do this advice is a corollary to the article, not a repudiation of it.
If you're a programmer, and you're paid well, don't assume that will last forever. Don't spend all your money (and beyond) on cars and rent. Invest as much as you can with the goal of being financially independent.
Not all advice is applicable to everyone. It's up to you to decide if you can and want to follow it. The advice was for young programmers and it is solid advice, but again, not applicable to everyone. It is applicable to a majority (probably even large majority). If you are young and earning a sw engineer salary it is very rare to not be able to cover your basic needs and have something left. Most people spends what is left in luxuries, lifestyle creep, etc; which is what the advice is trying to warn people about.