Why Do Some Listings Have Larger Product Images on Desktop?

Does anyone know why some Amazon product listings display images larger than others (on desktop)?

From my checking and testing:

- This isn't category related (listings in same category for same product have this difference)

- It doesn't appear to be related to uploaded image size or format (I've tested uploading PNG vs JPG and different image dimensions (all over 2000px square), varying them between the main image and product images)

- It's not related to age of listing because we have products of various creation dates that have this difference.

Any ideas?

Thanks in advance for your contributions.

I've attached a couple of random products below that show this difference in image size on the desktop product detail page.