Schwalbe has a pretty deep MTB offering, with four or five compounds of eight or more models over the last few years, which would explain why they account for about a quarter of the tires tested. Additionally, when a tire from a manufacturer tests really poorly despite being labeled as their “fastest”, it’s pretty easy to write that brand off, and I personally am not too interested in seeing each of their lesser tires tested(see Maxxis Aspen, IRC, etc…)