I think it’s an important distinction. Many people want to work on free software, but also have bills. So they think “How can I make money from doing this?”, which leads them down to a very limited set of options¹:

• https://www.gnu.org/philosophy/selling.html.en

• https://www.gnu.org/philosophy/selling-exceptions.html

But these are not the only means to make money! To return to my mountain analogy, you could easily imagine many ways to profit from the mere existence of a mountain. You could, as I wrote, give guided tours, but you could also build water slides, build an observatory at the highest peak, or mine the mountain for precious minerals. All these have some risk, of course, of damaging the mountain itself, but they are all money-making schemes which would not occur to anyone wanting to somehow profit off the mountain exactly as it is.

Therefore, calling it “making money from FOSS” is simplistic and limits your own thinking.

1. https://news.ycombinator.com/item?id=30293290