If I install Perl and Ruby on my XP box, will you call those Windows vulnerabilities?
You're missing the point. First, if windows has them installed then YES they are windows vulnerabilities. if you installed them and they didn't come with the isntall disk then no they aren't.
But I think the point is they are just using those as ONE way to launch the exploit. Kind of like using vbscript to launch an exploit to attack the real exploit. So it's not ruby that's causing the exploit it's just a mechanism by which they attack it.