yes, this setting missing because in fact does not needs.
Gallery returns array, if needs to get image IDs needs to use [‘ID’] as parameter, i.e. for example:
<?php
$images = get_field('gallery_field'); //gallery field
foreach( $images as $img ):
$img_srcset = wp_get_attachment_image_srcset($img['ID']); // return Image ID for each in gallery
?>
