Even if it is him, I don't think DHH would create a Rails based blog just for the purpose of posting pics of his pet project. DHH is a pragmatic guy, and Tumblr is an excellent tool.
Yeah, that's true. It's been a few years since the discussion but the 37signals blog was on Wordpress at some point (might still be) and pragmatism was cited. I agree with this and my own Ruby blog is on Wordpress too ;-) Ruby blog solutions mostly suck.
That has photos of the car under construction