My only suggestion would be to namespace your function as add_post_types() is pretty generic and could conflict with another plugin. Also you can make it a little more concise, like so:
function steel_add_post_types ( $post_types ) {
return array_merge( $post_types, [ 'glossary' ] );
}
add_filter( 'pb_supported_post_types', 'steel_add_post_types' );