Yahoo adds a little subdomains button

I’m not completely sure when this happened but it looks like Yahoo rolled out a small change to Site Explorer with the addition of a “Subdomains” button.

That “subdomains” button is pretty new – here’s what the the interface looked like according to this post on SEOptimise a while ago:

I don’t think it’s a big deal, though I’m not entirely convinced I know what the button is trying to do:

It looks like it’s a stab at a domain diversity metric – perhaps 142 total inlinks from 24 subdomains to my root domain. According to Linkscape it’s closer to 221 inlinks from 59 FQD’s. Any ideas? I admit, it’s been a long time since I last looked at Yahoo! Site Explorer.