That article literally refers to it as poverty line as well a bit further down. "Poverty line" isn't a thing, thing. It'll always require some math to localize.
Lower down it discusses the nationally averaged poverty line. At no point does it make any claims to a number for a SF specific localized poverty line. As you say, local values are going to be different, but the national number is far below the "low income" threshold set earlier in the article.