Scrolling in the Grid view works fine. I tried two different mouses to make sure.
This has never happened in any of the previous versions on the same computer.
If you're on Mac, under the Interface tab, you can uncheck and check the "Swipe between images using mouse/trackpad" to toggle the behavior. I believe there is a bug that if the Preference dialog isn't shown, the preference entry would not be initialized to preserve the legacy behavior.
It's very understandable that this particular thing broke with this upgrade. If you read earlier replies, one says that a new preference was added to control whether the mouse should scroll the thumbnails, but someone forgot to program in the behavior if that preference didn't exist.