Source

File: wp-includes/class.wp-scripts.php

public function set_group( $handle, $recursion, $group = false ) {
		if ( isset( $this->registered[ $handle ]->args ) && 1 === $this->registered[ $handle ]->args ) {
			$grp = 1;
		} else {
			$grp = (int) $this->get_data( $handle, 'group' );
		}

		if ( false !== $group && $grp > $group ) {
			$grp = $group;
		}

		return parent::set_group( $handle, $recursion, $grp );
	}