For a guy that thinks Linux isn't the right way for Valve to go, I can't comprehend why Carmack would agree to use Android considering it is Linux.
because they are 2 totally different things. what valve is doing is building a foundation for pc-consoles entirely dependant on a linux game library. support for the OS is rising and will probably skyrocket if steamOS is semisuccessful. Valve certainly thinks that linux is the future, but there are others who disagree and take the "we dont need any more fragmentation of the gaming market" approach.
android is another beast entirely as its pretty much the only open source option in the mobile market that is accesible to millions.