The Search functionality has not changed in a very long time, if ever. It is explained in detail here: https://www.manager.io/guides/16487.
If you had the impression it ever searched only for complete, literal strings, you were either updating from a very old version of Manager with far more rudimentary search capabilities or the impression was accidental (because you did not happen to have records with the right characteristics to see its actual performance.)
At any rate, there is no way to limit multi-word search criteria to literal strings. All separate words in the criteria function as though they are separate strings joined by Boolean AND operators. Quotation marks are considered part of the string.