Checking hydrometer accuracy with charged battery voltage

I do not see how. The longer a cell sits just after charge cessation up to an hour the higher the gravity climbs because the lag and over run tendency of chemical / electrical relationships. The electrolyte could cool and gain density but the other war round is hard to envision.

Then again I am assuming the measuring instrument is reasonably accurate. A .02 error to me is unacceptable. But an OEM releasing 1.300 FLA to the public would be even more disturbing. Oh well, that's life.