When I’m on an image page, if I touch the background and swipe up slowly, the tops of several thumbnails move into the page from the bottom before disappearing. Also, the browser’s scroll bar is showing the page is being scrolled but there is no change to the viewer...but I can see that the colours of the browser’s "menu" area is changing, almost as if there are blurred thumbnails being scrolled. The length of scrolling is directly related to the number of images in that folder.
On my Surface Pro: Firefox, Chrome, and Edge do not exhibit this behaviour.
In an image page, when I tap on "Photo Data" or the "Share" buttons, I get a message that you normally only get when doing a mouseover i.e. "Display photographic (Exif/Iptc) data" or "Share this photo over social sites". I then have to tap on the button again to get the desired pop-up window.
On my Surface Pro: Firefox, Chrome, and Edge go straight to the pop-up when I single-tap the relevant button (although Edge does very briefly show the mouseover message before displaying the pop-up).
Unfortunately none of my iOS devices is allowed for iOS11 upgrade... I should have buy a new iOS device again...
1. I don't see the point why would you scroll up the background in the lightbox.
2. That's the expected behavior. Browsers which support mouse too will allow you to perform the click action right away, while those with touch only interfaces will first perform the hover action first.