This blog post was posted in the comments, it is a great read too https://www.thomsonarchitecture.ca/2020/08/13/embodied-carbon-i-do-not-love-you/
I think sometimes (often?) with these claims it’s a case of the marketing team latching onto something and not appreciating the nuances of carbon accounting. Until we can develop truly carbon negative building materials the maths just isn’t going to work. With abundant renewable energy I think it might be possible, but until then reusing existing building stock as much as possible is the clear winner. I can still dream of my straw bale house using locally sourced clay render though.