To be fair it's one of the better ones. But yes, I have no idea how this reached the front page. This is like every other lightbox I've seen.
1. The parent plugin could attach to one element through the HTML changes. The JS change - you need to explicitly bind the lightbox to click event. In the current plugin - you do not need to edit any of the existing HTML. Just add one line of JS to view all the images (or probably a select few) in Lightbox on the page.
2. While providing this feature, it might not be evident to the user that clicking on the image shows it inside Lightbox. Hence the tooltip.
After re-reading the OP it seems like I should try it out next time I need to use a lightbox, though.
I think I just took the parent plugin handicap & fixed it. But guess Jquery plugin is already doing it the way I am doing it.
Thanks for pointing.