That just tells you whether data purity checks have ever been run and return clean, not if CheckDB has. If the DB was upgraded from 2000, it's possible for that to be 0 even with a clean checkDB having been completed a second earlier.

To see when CheckDB last ran without error, look at the dbi_dbccLastKnownGood which is the date that CheckDB last ran without error. If it's 1900..., the answer is Never.