Lets not conflate this with the M logo, which wasn't my point (I don't think either of us would expect the Tumblr logo to take you anywhere other than Tumblr).
The point, correct me if I'm wrong, of your post was that a company's logo on their Tumblr blog should go to their own website and not to the root of their Tumblr blog. Yet, because your blog is on Medium it's ok that none of the titles go to your homepage?
I want to find out more about you. I click on your picture, it takes me to a profile on Medium, which links to your about.me profile and your twitter profile (and mentions a twitter handle for Scoutize). I then have to click through those to find actual links to your personal blog and Scoutize. Why are you ok with this interaction but it's not cool for a company to do it with Tumblr?