I think this article slightly misinterprets Buffett a bit. In the broader context of his values and beliefs, I think this "rule" is about focus.
Buffett (and Bill Gates) have cited focus as the single most important factor in their success.
See also Buffett's 25/5 rule (he did not give it this name).
Basically, Buffett's belief is that by not having extreme focus, you dilute your most important asset, time, to a degree that you are unable to accomplish something meaningful in any one area.
His views on time and focus are pretty well captured by the snowball metaphor (with apologies to those who have never lived in colder climates):
"Life is like a snowball. The important thing is finding wet snow and a really long hill."
In other words, w.r.t. this discussion, it doesn't work to be changing hills with any frequency.
Sure, but if you haven't even started your snowball yet, it may not be in your best interest to deeply scrutinize the length of the hill and the wetness of the snow until you find the perfect setup; it may just be better to get started with a snowball and then iterate as you're rolling it down the hill.
I definitely think there's value in the entire "say no to almost everything" philosophy, it's just that I see it regurgitated without much thought all over the place. I'll meet someone who wants to be the next Bill Gates / Steve Jobs / ... / Elon Musk and who deliberately says no to everything been though they have no other options. They're just waiting for that perfect fit which may very well never come.
Buffett (and Bill Gates) have cited focus as the single most important factor in their success.
See also Buffett's 25/5 rule (he did not give it this name).
Basically, Buffett's belief is that by not having extreme focus, you dilute your most important asset, time, to a degree that you are unable to accomplish something meaningful in any one area.
His views on time and focus are pretty well captured by the snowball metaphor (with apologies to those who have never lived in colder climates):
"Life is like a snowball. The important thing is finding wet snow and a really long hill."
In other words, w.r.t. this discussion, it doesn't work to be changing hills with any frequency.