Don't think this is technically a bug. Blender's thumbnail view always worked like this, as though it was a list view. It selects everything in between the start and end point of the selection.

I think it's a reasonable idea to change it, but this is really just quirky/different behaviour rather than an actual bug.

I see. Well I think it is weird when box select selects something that is not actually in the box. Feel free to close this if you think it is not a bug.

This might seem like a simple complaint about a simple problem, but is not.

First examine what is happening. Where is the end of the list? It is certainly below the last items, but is also to the right of those stragglers. So the selections shown in the video start at the end of the list, go to some part inside the list, and then therefore encompass everything in between.

To do to it more intuitively requires a very different set of behaviours when in thumbnail mode. Imagine that the selection shown worked as requested. You would, in fact, want to drag from that right corner up more than one row. It’s not just about not including those stragglers at the left, but more about selecting discontinuous groupings. For example, selecting up the left column of the example list would select a group of every fifth element.

I'd love to see this worked on. The only small concern I have is that this task's description and "steps to reproduce" don't adequately describe the actual problem to fix.

The current code is selecting a beginning and ending position and including everything in between. This works great in a simple list, but not when there are multiple items per row. This instead has to be changed so that individual items are selected (as if you ctrl-clicked them) if they are touched by the selection rectangle. The target behavior should be the ability to start at the bottom-right of the list, drag to the top-right of the list and have it selected everything in the right-side column - so every 5th element in a list that is showing 5 items per row.