tl;dr: e-bikes with a steel frame optimized for cost are more sustainable that weight optimized aluminum bikes.

I'm not sure that's the takeaway since they also talk about the multiple motor and battery replacements an e-bike needs over its lifespan undoing the initial lower emissions to manufacture, or how a well-built aluminum bike can last long enough to offset the higher carbon footprint compared to a poorly made steel one.

It seems the article is really pointing out that cheaply made bikes are the "problem". Bikes need to be built better (ideally locally so that bigger repairs are then feasible) and have better, more universal serviceable parts. Get more people biking instead of using motor vehicles whenever possible, and stop making the "disposable" tier of bikes so that switch is even more impactful.