The article is largely talking about academic success (with one or two exceptions) which imo is much easier to normalize across countries. The context to this

The article is largely talking about academic success (with one or two exceptions) which imo is much easier to normalize across countries. The context to this article is that "grit" is used as one of the characteristics that charter schools and other educational programs in the US try to maximize in low performing areas. If "grit" can't be measured, or if it's just another way of describing another attribute (e.g., contentiousness, which is the article uses - or persistence, which is what you find in many academic articles), then there isn't much of a point of trying to maximize it in academic contexts. All of this assumes that school performance is something that educators want to increase. This may not necessarily be true in every country and in every context, but it should be true in most of them (and certainly in the US, where a lot of local governments are funding programs using these concepts).