The Mac equivalent (cmd+space to trigger spotlight, start typing, hit return) behaves as it should. If you move your mouse it'll highlight what is under it, otherwise the highlight stays on the top result as you type.
I use the keyboard shortcut "L" to label my mails. But because my mouse is usually somewhere around the location of the labels submenu before it even renders, I'll often apply the wrong label: the one at the mouse's position rather than the first one in the list. On a side note, starting to type actually hides the mouse cursor, so it took me some time to figure out why the 4th label was applied and not the 1st one.
Nothing beats accidentally creating a new class instead of adding an existing one as a reference just because your cursor was in the wrong place, then spending time on wondering why nothing happens.
If I start typing, in the address bar for one example, and my mouse happens to be resting over where the auto-complete will soon appear (as is likely because I just had to move the cursor to the address bar to select it) when I hit "enter" it will go to whatever my mouse cursor was over rather than what I typed.
The auto-complete box should detect mouse MOVEMENT not mouse position. The fact that my mouse was there before the auto-complete box even rendered should be a massive red flag that I am NOT selecting something in the list.