Why Chris Pearson's name was brought up in the first place is beyond me. I know for a fact that the Theme team was involved with the migration from Thesis to Genesis. The theme team has been known to do one-off migrations and doesn't necessarily make a living doing it. The situation and speculation that Carl talks about in his comments is valid.

When Matt Cutts switched themes last time, he wrote a post on his blog saying so. So far, I haven't read anything on his site concerning the latest switch. If it is found out that Matt C was approach by either Matt M or the theme team to move away from Thesis to something else, like Genesis, it's going to look pretty bad on Automattic's part. But if Matt Cutts decided to switch on his own and reached out to Matt M or the theme team on his own accord for help, then everything is fine.