Using MS as an example is probably not ideal as they have admitted that they design their product in such a way that it will always finish at the bottom of tests. Go back to the old statement they made about MSSE being a 'baseline' antivirus.
For what it's worth, the 360 thing about western users is the fact they use cloud technology that differs by area, so you may get slightly different information or results depending where you are in the world. They also say on their blog the testing houses knew in advance the Bitdefender engine was turned on by default in the version sent for testing. What the real truth really is, is anyones guess.
At the end of the day, there has been attempted falsifying and cheating at tests or benchmarks as long as they've been around, PC hardware manufacturers, phone makers, software, the list goes on. Nobody should make a judgment about whether they use a product based solely on benchmarks or tests like this, they are a tool to help gather an informed opinion but shouldn't the final opinion about the software itself.
On a side note, why do these testing labs have to use different versions of the software to the rest of us? Surely using the same download everyone else uses would stop a lot of the attempted cheating.