Last time this came up, somebody made the comment that you're in the highest category that you have finished everything below. Just because you started with git doesn't make you good at VCSs, but if you have done everything below it as well, you probably are an expert. To put it another way: would you put SVN on the right side of that row?
As an aside, I do believe that DVCSs are somewhat more complicated than their centralized counterparts. This is mostly because they are young and lack the mature tool environment that things like SVN do. As a result, users are forced to understand how they work, instead of relying on pre-defined sequence of work->save->test->commit. If SVN was the new hotness, people would have written reams about the theoretical motivations behind a a centralized server, copying-as-branching, etc. But it's not, so git/hg/bzr get all the credit for being algorithmically interesting. In the end, this means that if you don't want to think about it, go with a VCS that's a little older, and I think that justifies the ordering in the chart.
As an aside, I do believe that DVCSs are somewhat more complicated than their centralized counterparts. This is mostly because they are young and lack the mature tool environment that things like SVN do. As a result, users are forced to understand how they work, instead of relying on pre-defined sequence of work->save->test->commit. If SVN was the new hotness, people would have written reams about the theoretical motivations behind a a centralized server, copying-as-branching, etc. But it's not, so git/hg/bzr get all the credit for being algorithmically interesting. In the end, this means that if you don't want to think about it, go with a VCS that's a little older, and I think that justifies the ordering in the chart.