Dude, they literally lobby the government to prevent homes being built in San Francisco the densest place in the nation and the perfect place for parking lots to become housing towers.
In my lifetime of living here in San Francisco, the Sierra Club has talked a big environmental game and opposed all housing. In fact, I recall the first year I was interested in policy and was curious why SF finds things so hard. I remember my uncle having Sierra Club posters on his wall so I went to look. I remember very clearly Sierra Club endorsements https://www.sierraclub.org/san-francisco-bay/2015-sf-endorse...
I remember their opposition to 8 Washington. I remember their opposition to 75 Howard (which became 17 Steuart, I think). In fact, every single time push comes to shove, the Sierra Club has opposed housing. Explain this.
My family used to work in Cross-Laminated Timber and Dowel-Laminated Timber structural design, my man. You don't have to convince me about wood. We have encountered who stalls construction and who opposes specific projects while talking a grand game. And it's the environmentalists.
In fact, if you think the Sierra Club is a pro-housing group after I've seen them, with my own eyes, oppose housing on the grounds of shadows, lobby against pro-housing bills, and protest it, I really do question what you know about things. I don't mean this in an online "gotcha" way. I mean in actual practice. What do you know about the Sierra Club that is not from online research? If you only know them through online research, I can understand your confusion. Sierra Club BC is a very different game than Sierra Club in California.