Google is testing a new feature, the-recommended-group-to-join-fo">or search refinement, within the image search results that shows you “from this image.” I suspect this shows you matches of other image search results, from the image you are currently looking at.
This was spotted by Khushal Bherwani who shared this screenshot with me on X:
I am not able to replicate this but it seems that after you click on an image from the image search results, Google may show this new section to show more related images to the image you selected.
Forum discussion at X.