No the article is saying don't ever waste time fantasizing because it's the same as writing new features in code that no one will use. It specifically calls out things like buying workout clothes before you work out, or getting a new journal before you start journaling.
Maybe you missed the point of the article. The author is describing a common issue where people have lots of ideas, plan them out in their heads and get the reward in form of pleasure (anticipation of success, power, beauty, anything). They don't imagine or plan actually doing the work, they plan for wonderful outcomes. They never do what's necessary and become quite frustrated, not knowing why. There was even psychological research into this phenomenon if I recall correctly , and it yielded the somewhat surprising result that this is a strong habitual behavior and thus fairly hard to change.
Because the risk is that you will never start working out or never start journaling, so your purchase / planning was a waste. Adopt good habits before you invest in them.
As a programmer, I find "fantasizing" important, as in thinking ahead. I'm working on a program, and I do from time to time imagine my software being popular, widely-used in the future, etc.
I actually find it useful to, instead of immediately acting, sometimes take a bit of time to ask: how do I want my UI to look? How are people going to use this software? What are some typical use case scenarios? I've gained valuable insight by daydreaming a little bit, and not acting immediately.
IMO, you need a mixture of both some planning and also actively working on the project. You can get stuck in fantasies, design something overly complex that you think will solve all use cases (but actually does many things poorly instead of doing one thing well). You can also fantasize about a project so much that you get bored of the project before you even really get started.
The article is discussing fantasizing that does not result in action