Why should they be backed by Shimano? Canyon did the batteries with Trendpower ( former Simplo). Shimano was only opening their system to third parties. So they are not responsible for anything like design or quality issues…they have to replace them all, they told people to throw out bad batteries. so they have no way to even know if you kept yours or chucked it
does suck for them, but financially? their fine. These are backed by Shimano. Its a significant problem for Shimano since they are the ones responsible for replacing them.