from my rather long experience with the predecessor, the still "current" 300/2.8 SSSM, there has to be a mistake in the testing of the new Sony lens - it will not be worse than the old version (or will it?).
And the current 300/2.8 SSM is at least on par with the Zeiss 85/1.4 AF or the 135/1.8 AF which I use, and A LOT (and I mean: A LOT!) sharper than the Sony 35/1.4, for example - it is one of or even the best lens in the Sony system (for an impression, just look at Sony´s MTF charts).
Almost everybody in the Sony forums who has access to that lens says the same... - so could there have been a mistake?
A focus problem or a "faulty" lens, for example?
I would LOVE to see a retest with a second item - Sony company should be interested in putting the result right and proving the 300/2.8 SSM to be the "stellar" lens it is... - the current version is indeed!