To me the fact that he left there in January means lots of things could have changed since then.
Paul Matthews are still listed on Linkedin as being a member of the sapphire team.
And where did he leave? He left to work at Applied Materials. A company apparently heavily involved in the making of Apple's products:
http://mashable.com/2012/04/02/applied-materials-ipad/
Applied Materials are, among other things, also making tools to construct solar panels.