To my surprise the technician inspected the laptop and said that the keyboard was damaged (a few keys were wonky, remember the butterfly keyboards?) and that there was an official repair program for that. It turns out that the battery, keyboard, and trackpad is a single repair item. If you want to replace one, you have to replace all three. So instead of a battery replacement, I got a keyboard replacement which just happened to include a new battery and a new trackpad. At the beginning of last year the battery started to expand again and I went to an unofficial repair shop instead. They replaced just the battery for ~$150.