I had to do some serious digging on this. They previously listed the Chevy Bolt as expected to have good (not excellent) reliability in terms of batteries and motors. A few years later, reviewing their ratings for those same years, it dropped to very bad.
Once I filtered out the noise (and trust me, there was a lot), it seemed that they were counting recalls as failures. And to be clear, the Bolt had a very significant battery recall that drove most of this. But being a recall, these were all covered for free, and most of the repairs were done before failure (as parts became available).
While these were technically failures, they are not the type of data that people generally look for. I want to know how likely I’m going to be stuck with a repair bill (especially a big one), and how often I’m likely to be going in for service. Neither of which is covered by this data.