This is an attempt to find the diff between the latest English theme unit test, and Japanese theme unit test, then creating the xml for difference. Thereby creating the theme unit test posts containing new block test posts.
I have found that, basically, they are the posts dated after October 2018. So you can do wp export --start_date=2018-10-01 to exprt the posts that are different. In numbers there are 13 posts in total: 10 blck posts, 1 keyboard navigation post, and one scheduled post for 2030. en-theme-unit-test-post-oct-2018_2019-07-30.000.xml file is this export as of 2019-07-30.
block-posts-partly-translated.2019-10-31.xml is a partially translated file of above. There are 13 in there, including non-blocks. Seven are translated. Fore more to go. Also two that has not to do with this, nees update.
theme-unit-test
Theme Unit Test
For instructions on how to use the Theme Unit Test please see https://codex.wordpress.org/Theme_Unit_Test
Note that issues and pull requests for the theme preview file will not be reflected on WordPress.org. This file is for testing only.