> In other words, in science and math education in particular, it’s easy to slip into teaching methods that emphasize understanding and that avoid the sometimes painful repetition and practice that underlie fluency. I learned Russian not just by understanding it—understanding, after all, is facile, and can easily slip away. (What did that word понимать mean?) I learned Russian by [...]

This is a misleading use of 'understanding' being equated to remembering.

The thing that made math so much easier to learn for me was that as soon as I understood a concept or method of logic, it was effortless to internalize and recall. Things that only depend on 'facts', like the meaning of понимать is what can't be understood and must be remembered. But if that was your native (or closely related) language it could be understood by seeing its roots and construction.

The hard part is getting someone get a foothold in an unfamiliar subject so that other understandings can be built upon it. What the author seemed to have done is two things: turn an aversion into an interest and realize that they can actually learn math, not merely memorized.