I wish the tags would automatically populate when you used one of the shortcuts just as they do when you click on the UI.
There should be no difference between the two ways if you enter a space after the special character.
This only works if you put the special character in the beginning and not at the end e.g. if I type "hacker news %" it still only filters by open tabs, but it doesn't show the "Tabs x" label (whether I add a space or not). Which is how I use it 99% of the time, since I only need to add special characters if it wasn't already finding what I meant without them.
(Not that I mind personally, since I'm already familiar with the feature)