add_image_size is intended to be defined globally (outside of the context of a post type). This is because when images are generated they are not yet attached to a specific post type.
If you’re using a plugin or WP CLI to regenerate the thumbnails, you are outside of the context of a post type. Therefore those checks are always going to fail.
You should simply do
add_image_size('75x75',75,75, true);
add_image_size('150x150',150,150, true);
add_image_size('200x200',200,200, true);
add_image_size('400x400',400,400, true);
In your functions.php, class file, plugin, etc.