WP 6.3 introduced the notion of enqueueing Javascript scriots with the Defer attribute to give a performance benefit.

Since the plugin script provide funtionality that is only invoked after the page is loaded (as code is invoked on the basis of user interaction), the plugin code can take advantage of this.

Following the advice given in WordPress Core, because the parameter used for WP 6.3 will be treated as true - the previous value. Therefore this coding will work as previously with older versions of WP.