How to use "Is one of" operator in exposed filter?

Hi
I have set exposed filter Content:has taxonomy term.
I have set operator to "Is one of"
How it is suposed to work?

When I type in filter two words, for example "London city" it should search for terms "London" or "city".
But it is searching for one term "London city"
I t should search for two words separately, I am right?
After submitting exposed filter I see message that "London city" term was not found.

I have nodes with term "London" but they are found only when I type just one word "London" not "London city".
I have argument in URL as follows: myweb.com?region=london+city

How can I set "is one of" operator for one single textfield?

thanks for any advice