I think it is a misguided attempt at making the content dynamically adjust to the device proportions, so the screenshot is large but not overlarge (over screen size) on mobile and desktop devices of different orientations. A laudable goal, if badly implemented (I can't scale at all on mobile, it distorts oddly when I zoom on desktop).

Either that or deliberate user filtering: if you can't figure out right-click (or long press) then "open in new tab" on your own, then maybe you are not the class of user the creator wants to support :-).

I doubt the inconvenience is deliberate, more a side effect of some other design consideration. There are smaller images on each of the widget description pages (though they also scale oddly in places) which in total provide more detail than that one image. Perhaps drop the author a polite message suggesting that they include a "view full image" link near the screenshot on the opening page or with the image itself as the mouse target?