This is not unique to the web and does also apply to the app.
On courses that have multiple images, when one is shown an image [eg painting] and one has to answer with the right pairing (selected or typed) [eg artist] one is shown one of the several images available - ie a different one each time.
However I have noticed that when reversing the process, ie shown the answer [eg the painter] and asked to select the correct painting from four, the artist’s painting is always the same one - the first one that is shown when looking at the level. (However if you preview the level you will be able to see several paintings.)
Have a look at level 7 in this course:
but to really experience the problem, you will have to learn the five items first.
PS When learning, one is shown an ‘item’ (pair) both ways.
When one is shown a painting (any one from a selection available) one can NOW scroll through all paintings to find one that one recognises (making remembering an artist easier as some may be tempted to only learn one painting).
The same is true of map courses or nature courses that have multiple images.
When one is shown a painting to select the artist, one is only ever shown the one painting (despite several being available).
It would be nice if in this instance another from those available was shown.