Nick, XR aims to tell the truth - and that's the science on climate change. And then act as if the truth is real. That's not the same as "believing that they know best." Maybe, "believing that the climate science community knows best."
If I had been there, I would have been one of the 75% of polled XR members who disapproved of that action. But XR's structure gives autonomy to any affinity group that wants to do an action. The strength is flexibility and fast response - the downside is occasional stuff-ups. But note that XR is not there to encourage people to use public transport. Its aim is use disruption to force the government to accept the direction of a Citizen's assembly, or failing cooperation to depose it. "This is an emergency".