Fully agreed with you on the rigor regarding notation, really good progression of teaching (pacing and order in which the material is introduced), and soviet math textbook exercises being well thought-out and entertaining.
Very much disagreed on the rest, as my main personal gripe with learning math+physics in Russia was that there was zero emphasis placed on understanding of principles and logic and 100% on memorization. I spent 3 years taking physics classes there, and I learned effectively nothing, having to relearn it from scratch in the US. And that was the moment where I truly felt I understood what was going on, instead of treating physics as just another memorization exercise for a variety of random unrelated formulas. Similar with math, but to a lesser degree, because with math I was personally invested and was trying to understand the material rather than memorize, despite it hurting my grades in Russia greatly.