I agree with the article regarding numeracy and basic math foundation-- at least for my seven year old. It has been key to his enjoyment and facility with math- just understanding calculation and quantity.
When we moved him to an early-grade Montessori school, I thought the materials might be tortuous because he was working so comfortably with equations. It's been an unfounded worry- he loved the materials because they visually show him the number relationships. In fact, his mental calculation skills are much faster after working for 1/2 year on materials.
For DS, excellent math skills have been a combination of strong numeracy foundation, practice, and because of his "giftedness" providing higher level, interesting concepts at home (patterns, perfect numbers, interesting number sequences).
I was a victim of poor teachers, spotty math foundation, and no one explaining the effort it might take to excel in math (I was a "natural" at reading/language arts, so assumed I wasn't "good" at math because I had to work harder).