@mkismy is a member of the Japanese community and discussed this issue in advance in the Japanese Slack channel. I think this change makes sense, at least for Japanese.

In English, there are always spaces between words. Perhaps text-wrap:balance takes up that space and never cuts the word.

In Japanese, on the other hand, there are no spaces in sentences. We divide words by mentally determining whether they are nouns or verbs, etc. based on the context of the entire sentence and the surrounding characters. However, text-wrap:balance doesn't seem to be ideal, at least in Japanese, and can sometimes cut off text that it recognizes as words.

If line breaks are required, we have the option of injecting a br tag on GlotPress.

If we add this, it changes the balance of headings on the homepage, too. I've taken some screenshots of this PR applied to my sandbox, so you can see it on real content. Does this still look like you expect?

Home	Alt heading 2	Alt heading

On the news & single pages, it looks like this:

Thank you for showing me the screenshot. To me, all the screenshots all look as expected.

Just to be sure, I will send a ping to @miminari and @nukaga who were involved in creating the Japanese version design file.