Attachment Page nav is buggy?

Someone brought this to my attention when they were using my theme and I went to try it with my theme on my demo site as well locally. Sure enough this is what is happening…I have a WordPress gallery (using the shortcode) that has 2 rows of 4 columns (8 images).

Click on the first one and it loads it in the image.php page and you can now navigate through the rest of the images for that gallery. Get to the last row, image #3, the “Next” link disappears but the “Previous” shows. There should be one more image to view. Likewise, if you click on the last image, the “Previous” link now disappears.

I then proceeded to test this with the Twenty Twelve theme thinking is it something to do with my theme. Sure enough, it happens in Twenty Twelve too.

So am I correct in saying there is a navigational bug in WordPress? I have not tried this in 3.6, but in 3.5x yes.

For an example, check out my Preference demo:

Demo Gallery

I even added the twenty twelve nav code in my theme and still the same issue:

<nav id="image-navigation" class="navigation" role="navigation"><span class="previous-image"><?php previous_image_link( false, __( '← Previous', 'twentytwelve' ) ); ?></span><span class="next-image"><?php next_image_link( false, __( 'Next →', 'twentytwelve' ) ); ?></span>
</nav><!-- #image-navigation -->