The article doesn't seem well-sourced (their graph is a screenshot from a slide that says "confidential", and you can't make out the text that might be a refere

The article doesn't seem well-sourced (their graph is a screenshot from a slide that says "confidential", and you can't make out the text that might be a reference). But the point was that the chassis isn't a big part of the footprint which isn't contradicted by their claims. Note that the slide is not talking about the same measure (co2), the slide screenshot is titled "total environmental system damage" which smells a bit like picking an rarely-used but favourable metric here.