I recall having a conversation about this with an investor in the early 90s or so. He told me that a five-year projection was horse-apples, but he also insisted we do one because the exercise of guessing is valuable in and of itself, and he wanted to see evidence that you tried to think things through.
"In preparing for battle, I have always found that plans are useless, but planning is indispensable." –General Dwight D. Eisenhower
There's a similar concept in PhD programs when they make you present a timeline for future research. Every grad student knows that over the course of 2-5 years things will break, experiments will fail, people get discouraged, interests change, money runs out, whatever...but for the sake of completeness and forethought, they require you to detail future milestones. This stage of planning proves to people that you are committed to what you are doing and are in it for the long haul.
I think there are different monsters. One thing is to project what are you going to do in the next five years and another completely different is to forecast what are you going to "sell". I think the post implies that the later is crap. For the former I imagine that all of us know that things are going to change (as I think you imply too about a PhD program).
"In preparing for battle, I have always found that plans are useless, but planning is indispensable." –General Dwight D. Eisenhower