When pulling the Prospect - Rating in a Query, it is not possible to search only for up-to-date Ratings.
For example if a constituent has one older Rating called "X" and one up-to-date Rating called "Y", and now you want to pull all constituents who today have the Rating "X", the constituent from above is being shown. This is correct behaviour, because he indeed does have that Rating. But it is not helpful if you can't differentiate between historic Ratings and the up-to-date ones.