Not sure this is going to be a worldwide thing.
When you will have an issue with the specific canyon battery, there is really no guarantee that the partner you will find will be able to do anything and even more cope with warranty. They will look at it, potentially, but as it could be a totally different design it might be hard. If Canyon does not sell spare batteries, there might be some reason.
It guess this is not different than saying, oh let's ask an electrician to see if he can do something like replace some cell. Pretty hard to find these days to find skilled people.
At the very least with canyon: 1. you cannot buy a spare custom battery, 2. Even if you could it would be hell expensive 3. if something happens past Canyon warranty - which comes pretty fast - your bike is in the best scenario a brick for a long long moment, worth, dead.
This industry is a total mess, you cannot expect people spending 5-10k and have potentially no way to use it within few years.