WordPress: After Gutenberg plugin migration to block.json the localization/ translations with PolyGlot in JavaScript does not work anymore

I made a plugin with existing localization on WordPress.org for free. I migrated to block.json and made all changes by comparing it to the output of npx @wordpress/create-block todo-list. I read through the Block Editor guide on internationalization but there seem to be a few differences to the way it works in the todo-list example.

The result is that all my __ php functions work and translate all strings. But my __ JavaScript function does not translate any of the translation on translate.wordpress.org

What I tried and checked:

1. block.json contains textdomain: simpletoc
2. edit.js contains import { __ } from '@wordpress/i18n';
3. plugin.php contains Text Domain: simpletoc

I did not change it, but I use the __ function like this:

ToggleControl
                label={__(Remove heading, simpletoc)}

The sad thing is that it worked before in version 4.8 without block.json but I want to avoid reverting to that. Amazingly, the description in block.json does get translated but not the __ functions in the code. I tried to use some things before doing that:

In the init hook I tried to use

function register_simpletoc_block()
{

  wp_set_script_translations( 'simpletoc-js', 'simpletoc' );

  register_block_type( __DIR__ . '/build' , [
    'render_callback' = __NAMESPACE__ . '\\render_callback'
  ]);
}
add_action( 'init', 'register_simpletoc_block' );

I tried this but it does not work either:

wp_set_script_translations( 'simpletoc', 'simpletoc' );

or

wp_set_script_translations( 'simpletoc-toc-editor-script-js', 'simpletoc' ); 

since this is the script in the edit page of Gutenberg

But since I do not set simpletoc-js anymore, I have no idea if this is necessary. It would be really great if someone could explain or at least help me to debug this.

This is always empty:

script id='simpletoc-toc-editor-script-js-translations'
( function( domain, translations ) {
    var localeData = translations.locale_data[ domain ] || translations.locale_data.messages;
    localeData[].domain = domain;
    wp.i18n.setLocaleData( localeData, domain );
} )( simpletoc, { locale_data: { messages: { : {} } } } );
/script

If I install my old 4.8 plugin this part contains data from translate.wordpress.org as usual.

• This tag works: https://github.com/mtoensing/simpletoc/archive/refs/tags/4.8.zip
• This tag does not (block.json) https://github.com/mtoensing/simpletoc/archive/refs/tags/5.0.1.zip

What am I missing?