If by this site you mean Thundersplace, then no, this site is not pushing any specific extender, or any devices at all for that matter.
If this site is pushing anything, it is a free, hands on manual approach to PE. :)
sorry. But by pushing I mean, to me more then half of the success stories or advice given to someone about which extender to use. X4 seems to be the first second and third option. Other extenders doesn’t get the attention that one seems to get, which I’m sorry to say makes one question the honesty about people who say they gained from an extender especially x4. I say this all the time, if all extender work on the same principle it should not matter cheap or expensive. I could be wrong its just an observation