Why doesn't a dash search show me all results?

I've been using Linux for quite a while now but I'm new to Ubuntu and Unity. Just installed 16.04 and it's generally fine. However, when I search in the dash I can only find results for whatever's set in the 'filter search' section of the window (applications or files etc) - surely I should be shown the widest search result before filters are applied?. What I would like is to be given the first few 'Applications' results, the first few 'Files' results etc. From screenshots, I think there should be an 'All' option under 'Categories' but there isn't, and I can't see any way to get one. I like Unity as a whole but this dash behaviour seems counter-intuitive - either something's not quite right or I'm doing something wrong! Any help would be appreciated - cheers, Rob