> I'm irked by this because this is something I've been constantly correcting people with, mainly to indirectly challenge English-language exceptionalism (anything not Japanese is English - we don't know the French or German titles yet),

This is needlessly pedantic. By that logic, your use of Romaji is "incorrect" and Euro-centric exceptionalism, because the official original movie poster uses Hanji/Katakana. (And in fact, it'd be "incorrect" to say it was released in Japan, because in Japan, they'd say it was released in Nippon.)

It's an English-language article about a Japanese movie. Saying "titled 君たちはどう生きるか and renamed The Boy and the Heron for the international market" would make no sense because the audience of English readers won't be able to make sense of it.

It's not "English-language exceptionalism" to provide information in English when writing for an English-speaking audience, especially when it's clear in context that the information is a translation.