Those two counts were coming back empty. They are behind a login, and getting them needed the exact headers Pinterest's own site sends.
Pinterest pins were saving with saves and repins but no reactions and no comments. Those two live behind a login, and every attempt to fetch them came back null.
It turned out not to be an IP or proxy problem at all, which is what we spent the first day assuming. The request simply needed the internal handler headers Pinterest's own front end sends. With those, it works directly, with no proxy involved.
The extension also extracts the image, title and video from the page itself now, and skips promoted pins, which were being saved as if they were organic.