Actually you're not wrong about the phrasing innit. We should fix that.
The excluding words thing was to allow for things like BertieBotts's beans NOT heinz. On our form you'd put beans in match and heinz in exclude to get that result.
Search may be due a bit of an overhaul but we've got a list as long as a very long arm of things to do at the moment, so it might not get much attention for a bit.