I've also found DxO's camera sensor tests to be quite meaningless, when relating to the real world. They don't weight the criteria used in their tests well, imho. Often sensors which are given 'high' DxO ratings, don't perform as well across a number of 'real life situations' as other sensors which are given lower DxO ratings.
There are many other websites that cite themselves as professional, systematic, etc - whereas there are SO many variables, and if they don't get 1 thing just 'spot on' - it can ruin the overall results. I recall one site that tested scores of lenses, but many of them at their very minimum focusing distance (MFD) - where some lenses (even high quality ones) are not at their sharpest... and the results were very skewed.
Another site I came across a few weeks ago - the testers only tested the 'minimum focal length' (eg 70-300mm @ 70mm - and all at f8) - and only a certain 'part' of the overall image (centre pixels). It was crazy how some average quality lenses were ranked the same as others which were much higher, just based on that.
I have a marketing management and accounting degree, so I understand about corporate logos, branding, sponsorship, 'marketing words', etc - very well. So that could be an issue... but I doubt that DxO would test eg Nikon more favourably just because of that (they could open themselves up to legal action if that were the case....)
Having said that, I do like DxO's Optics Pro software a LOT. So I'm a customer of DxO's. I won't be so 'put off' by the annoyances I have with DxO's sensor test not to use their good stuff!