Note that Google's collection doesn't seem to include all of their extensions. For example, they are missing Google Voice, Google Dictionary, Send from Gmail, Page Analytics, Google Tone, Chrome Web Store Launcher, RSS Subscription Extension, Google Scholar Button, IBA Opt-out, Google Mail Checker, Google Similar Pages, Endpoint Verification, Chrome Remote Desktop, Chromebook Recovery Utility, Certificate Enrollment for Chrome OS, Screen Reader, Print, Google Docs Offline, and I'm sure there are plenty of other Google extensions that I missed in my search. Some of them have been abandoned for a number of years.
Also, this site [1] has been tracking Manifest V3 migration, but I think they might be incorrectly including Apps and Themes in their counts (I believe the 180K figure represents all of the items on the store [2]) which might be throwing off the numbers a bit.
[1]: https://chrome-stats.com/manifest-v3-migration
[2]: https://www.debugbear.com/blog/counting-chrome-extensions