Wow, that isn't what I see at all. I always have at least a single tab, even if it is untitled, and all tabs are the same width. Maybe you're on Yosemite? If so, this could a Yosemite thing. m.
Thanks, I see the issue now. I thought this was new to 2.01 beta 1, but I now see the Tabset was redeveloped in 26th Sept release
It seems I had "Document Tabs: Show for single document' unticked (or it defaults to false) Weird I've only just noticed, I always update TM as soon as a new ver is available