In other words, there are nine states, however that statistic is nearly meaningless. CA and TX alone count for about a quarter of the nation's population; altogether probably a third of the population is domiciled in community property jurisdictions.

Also, the states of Tennessee and South Dakota have passed elective Community Property Laws, so even your "less than 10" statistic is not unquestionably accurate.

Sure, but notably not the majority. It's predominantly a west / southwest thing. So GP's advice should caution that that specific legal advice doesn't apply to most people in the US.