Well I cannot have a really definite opinion on epubs and img tags as I'm in no way an expert. You are surely right and all the examples I've posted are somehow defective,
even if they come from real books!!!
I expected (and I suppose the book editors too) that
height:100% should be fine and as you say probably it's not. (BTW: 100% relative to the containing element, so if there were paddings or margins in
body,
div or
p, they should restrict the available area for the image).
But then we return to the final reasoning of my first post. OK, ACCESS is ignoring the img properties because they are defective, against specification or whatever. Even if other apps render they fine, you cannot say ACCESS is buggy because of this decision, because the epubs are already defective.
So, now we have 5 books (one of them, "The Last Empire" coming from Kobo itself...) with no valid image settings in the cover. Then what I really cannot understand is why Kobo is making a
height:100% fit when the image is smaller than the screen and a
width:100% fit when it is bigger.
The correct decision should have been a
height:100% fit when the image was
taller and narrower than the available area on the screen and a
width:100% fit when the image was
shorter and wider.