(See inlines at D3774)
Currently, dropdowns are inconsistent: hovering with the mouse doesn't immediately select the new item, however, pressing up/down/home/end / any key in 'fast access' does. Further, there is an 'anchoring' logic to the highlighted element.
This changes all that so that these commands just change the highlighted/hovered element. You have to actually press 'enter' to select it.
I feel like that's more in line with what dropdowns are expected to do, and doesn't change _much_ in general.