Depends on their methodology. Sure, a huge proportion of those are users who haven't heard of uBO, but we're forgetting a lot of caveats:

1. Electron exists and lots of apps are built on top of it and identify as "Chrome". Judging by the numbers most have been weeded out, but some edge cases do visit more sites so they end up in the count.
2. A lot of workplaces mandate the browser, which is often Chrome. This also gets counted.
3. A not insignificant amount of Firefox users change their useragent to Chrome.

All of these skew the numbers towards Chrome. Some Chrome users use a different adblocker which lowers the uBO statistic.