Tesla is actually starting to make cathodes in house via a dry process, which is why they are no longer buying cathode material from this supplier. Typical sloppy reporting from Electrek.
For many applications, like web backends that may have previously been written in Ruby, Python, or JavaScript, the garbage collector was not noticeable at all. Improvements to the garbage collector target apps that previously would have been written in C with manual memory management, as mentioned in the talk. Not all apps need to be written in C obviously, but this will help bring Go's concurrency primitives to places where the GC was previously a deal breaker, such as eggnet's program.