Update… I even tried to add the icon as an svg, and it still had the same delay loading.
// Custom FiboSearch search icon
add_filter( 'dgwt/wcas/form/magnifier_ico', function ( $html, $class ) {
$svg = '';
ob_start();
?>
<svg xmlns="https://www.w3.org/2000/svg" height="14" width="14" viewBox="0 0 512 512"><!--!Font Awesome Free 6.6.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free Copyright 2024 Fonticons, Inc.--><path fill="#888888" d="M416 208c0 45.9-14.9 88.3-40 122.7L502.6 457.4c12.5 12.5 12.5 32.8 0 45.3s-32.8 12.5-45.3 0L330.7 376c-34.4 25.2-76.8 40-122.7 40C93.1 416 0 322.9 0 208S93.1 0 208 0S416 93.1 416 208zM208 352a144 144 0 1 0 0-288 144 144 0 1 0 0 288z"/></svg>
<?php
$svg .= ob_get_clean();
return $svg;
}, 10, 2 );