再利用ブロックのショートコードでimgタグのwidthとheightが付加されない理由とは？

<?php
function call_back($buffer) {
    
	if(is_singular('report')){
		return _image_dimensioning_filter_content_tags($buffer);
	}
  return $buffer;

}
function buf_start() { ob_start("call_back"); }
function buf_end() { ob_end_flush(); }

add_action('after_setup_theme', 'buf_start');
add_action('shutdown', 'buf_end');

//https://xakuro.com/blog/wordpress/2185/
function _image_dimensioning_filter_content_tags( $content, $context = null ) {
	if ( null === $context ) {
		$context = current_filter();
	}

	if ( false === strpos( $content, '<img' ) ) {
		return $content;
	}

	if ( ! preg_match_all( '/<img\s[^>]+>/', $content, $matches ) ) {
		return $content;
	}

	$images = array();

	foreach ( $matches[0] as $image ) {
		if ( preg_match( '/wp-image-([0-9]+)/i', $image, $class_id ) ) {
			$attachment_id = absint( $class_id[1] );

			if ( $attachment_id ) {
				$images[ $image ] = $attachment_id;
				continue;
			}
		}

		$images[ $image ] = 0;
	}

	foreach ( $images as $image => $attachment_id ) {
		if ( $attachment_id ) {
			$size = array();
			$filtered_image = $image;

			if ( false === strpos( $filtered_image, ' width=' ) && false === strpos( $filtered_image, ' height=' ) ) {

				if ( preg_match( '/src\s*=\s*[\"|\'].*?-([0-9]{2,4})x([0-9]{2,4})\.(jpe?g|png|gif)[\"|\']/i', $image, $s ) ) {
					$size = array( $s[1], $s[2] );
				} else {
					$s = wp_get_attachment_image_src( $attachment_id, 'full' );
					if ( $s ) {
						$size = array( $s[1], $s[2] );
					}
				}

				if ( $size ) {
					$filtered_image = str_replace( '<img', '<img width="' . $size[0] . '" height="' . $size[1] . '"', $filtered_image );
					$content = str_replace( $image, $filtered_image, $content );
				}
			}
		}
	}

	return $content;
}

<?php
add_action(
	'snow_monkey_prepend_footer',
	function() {
		echo apply_filters( 'the_content', get_post( 12345 )->post_content );
	}
);