manage_{$taxonomy}_custom_column is a dynamic hook, so until you are using a proper value for $taxonomy like post_tag, it would work perfectly.
Adam Brown page tells it as deprecated because it looks for exact match, while there is a change in the files so the current hook being used are manage_{$this->screen->taxonomy}_custom_column or manage_{$screen->taxonomy}_custom_column which accepts the same value whether it is post_tag or something else, and that’s the reason you don’t get error or warning.