What does it mean "OSNMA is data authentication not PVT authentication"?

GNSS authentication is achieved by incorporating specific features that cannot be predicted or forged by malicious actors in the broadcast signals. A receiver enabled for authentication can interpret these features to distinguish genuine signals from imitations. This can be done at two complementary levels: at the data level, to authenticate the broadcast navigation messages; and at the range level, to authenticate the measured ranges to the satellites. The combination of both data and range authentication allows the computation of an authenticated PVT solution. OSNMA service provides authentication at data level.

OSNMA will be complemented by the Signal Authentication Service (SAS), which will offer range authentication in the E6 frequency band. The OSNMA bits, which are partially unpredictable, can be also exploited by receivers to provide some level of protection at the range level.