For the media query I changed it to
@media all and (min-aspect-ratio: 1/1)
When I toggle in dev tools to device mode and select responsive, this works as I expect. In other words, if the width becomes as large as the height, the thumbnails are moved to the left.
However, when just viewing the page in chrome (split screen on monitor – so taking up right half of the monitor), the height is certainly bigger than the width and the the thumbnails are on the bottom. As soon as make the window a little wider or a little shorter, the thumbnails move to the left. This happens well before the width catches up with the height. So I guess the question I need to ask is how is the aspect ration calculated here? It seems different than what I saw for the responsive mode, where an aspect ration of 1 was a square sized window.