Thank you for your valuable contribution.

Hi,
the documentation you are refererring to is for register_block_pattern() only.
When we place patterns inside the patterns folder, register_block_pattern() is not used, see https://developer.wordpress.org/reference/functions/_register_theme_block_patterns/
https://make.wordpress.org/core/2022/05/02/new-features-for-working-with-patterns-and-themes-in-wordpress-6-0/

It would absolutely have been easier for the developers if the two methods were more consistent, but now it has already been documented as yes/no and not true/false and it will need to continue to support yes/no.

It seems something has broken in 6.4. I would like to learn if this is only something on my local install, or if it can be reproduced, because then we have to create a new issue in the Gutenberg repository.

With 6.4 beta 2, current nightly:

If I add Inserter: false OR Inserter: no to any pattern in the patterns folder that is not already hidden, like if I update patterns/hero.php in my code editor, save the file, and then create a new post or page, that pattern remains available to me in the inserter.
Similarly, if I update the categories value for the hero pattern, the category does not change in the editor.

Thank you @carolinan for the explanation.

It seems something has broken in 6.4. I would like to learn if this is only something on my local install, or if it can be reproduced, because then we have to create a new issue in the Gutenberg repository.

Are you using the WP_DEVELOPMENT_MODE constant with theme as value?
https://make.wordpress.org/core/2023/07/14/configuring-development-mode-in-6-3/

I can't reproduce that when WP_DEVELOPMENT_MODE is used.