That makes sense to me. Now that I think about it there are a lot of mathematicians in the US doing maths in English who learned in some other language, and you

That makes sense to me. Now that I think about it there are a lot of mathematicians in the US doing maths in English who learned in some other language, and you never hear complaints about limitations of English. But I think the thrust of the article linked here was "are there ways it could be easier for children" rather than "are there ways it could be easier for grad students and professors". I'm not sure the answer to the first question is "yes" but it seems plausible at least.