Ngl, I find this so confusing. Back in the day the figures quoted would have been for vinyl and cassette sales. The figures quoted these days, does that include CD's? Streaming?
And, yeah, it's never entirely clear whether it's US sales or worldwide sales that are being talked about. If it's worldwide then it clearly will have sold more than the Eagles. The Eagles were great but, come on! If it was a Beatles album that had sold more that would make sense but the Eagles? Hardly.
I've seen suggestions over the years that the 100 million figure includes sales for the various singles released off the album. I've never checked the Guiness Book account of this, what data are they using so I don't know if that is true.
I need a nice simple story, lol.