[wmf]

The last release of OS X was 11 years ago but this site shows it having over twice as many users as macOS. It's totally implausible.

[Caligatio]

I haven't done any investigation but some scraper and/or bot configuration uses OS X as its user agent.

I run an unpublished service used by 1s of people and was hit by an influx of supposed OS X user agents that didn't correspond to my actual user base.

[fragmede]

Did you run any advanced TCP fingerprinting techniques to dig a bit deeper?

[kelnos]

Regardless, they're the same OS, so any serious (read: competent) person compiling stats like this would combine them into the same bucket.