I'm not really surprised. Michael has been recommending linux users to nvidia for years and has repeatedly proven how their closed source drivers are so good that they sometimes outperform Windows. Michael also rarely seems to have complaints about nvidia products. While phoronix is relatively small, there aren't many websites where nvidia is #1 in most tests, so it'd be stupid of them to not do favors for Michael. Despite all of this though, I appreciate that Michael isn't completely biased towards nvidia, and seems to praise AMD's open source efforts.
Their reasons for new Tegra porting have nothing to do with Phoronix.com but internally they use PTS for ARM performance testing so they need it to work, same for many other PTS Commercial users.