"The code" here you're referring to (fetch_extension_names.js[1]) isn't and doesn't claim to be LinkedIn's fingerprinting code. It's a scraper that the researcher behind this repo wrote themselves in order to create the CSV of the data that they're publishing here.

LinkedIn's fingerprinting code, as the README explains, is found in fingerprint.js[2], which embeds a big JSON literal with the IDs of the extensions it probes for. (Sickeningly enough, this data starts about two-thirds of the way through the file* and isn't the culprit behind the bulk of its 2.15 MB size…)

* On line 34394; the one starting:

    const r = [{
                id: "aacbpggdjcblgnmgjgpkpddliddineni",
                file: "sidebar.html"

1. <https://github.com/mdp/linkedin-extension-fingerprinting/blo...>

2. <https://github.com/mdp/linkedin-extension-fingerprinting/blo...>