It is automatic AFAICT. But a difference between the plugin and 5.1.16 is that the plugin also
inserts empty space below the bottom-most tiddler so that also bottom-most tiddlers align with the viewport top edge. While I'd wish for this behaviour also in 5.1.16 so that really *every* tiddler clicked on aligns with top, this is unfortunately not the case. Is it this issue you're having? If you really think this is important then I guess you'll still have to use the plugin.
<:-)