I don't see this as an arms race at all. (Heck, it took a major outcry just to convince Mozilla to show the version number in a place where normal users could find it.)

I agree that it's a redefinition of what "version number" means: now it's essentially date based, rather than feature based (though the two are obviously correlated). But I can't see any obvious reason to read "redefinition" as "corruption". It's just different, and both Mozilla and Google had sensible reasons for making that change.

In fact, their decisions may make it worth questioning those assumptions more broadly. Is there a chance that your version numbering method is causing subtle problems for your own development process?