Thanks for your interest in DxOMark.
Sony lenses we analyzed were provided by Sony itself. About your remark on the 35mm f/1.4, analyzer results confirm what you noticed (please check the comparison here Sony 300mm vs 35mm f/1.4).
If you only look at the Sharpness score, the 300mm is far higher rated than the 35mm f/1.4. However the DxOMark score is performed lowlight. In such condition, the larger aperture of the Sony 35mm f/1.4 enables a lower noise on the SLT A99 sensor. That means that you will finally get a similar IQ on both couples: on one side (300mm), you have a sharp image but with an higher level of noise, on the other side, the image is softer but without noise.
The DxOMark team