Interesting. Help → About works also in Linux. Although it’s difficult to find, since they hided the menu bar by default in that release. TorButton however still advises to download from torproject.org. I guess they will fix that in next major version.
A separate Tor Browser Updater still makes sense. For initial installation of Tor Browser as well as for clean re-installs.
Oh yes, I use classic theme restorer to bring TBB back to some semblance of a decent UI so forgot about the whole hiding menubar by default crap.
For initial installation you probably don’t need an updater, just include the latest TBB at the time of release though for clean profiles it would come in handy (and may also be useful if a change happens that TBB’s updater can’t handle, at the moment it’s only mac users who have that in their future).
I don’t think it’s a good idea to use the theme restorer. Remote websites can likely detect this due to different browser window size. Unless The Tor Project fixed that issue it is recommend against to change this. Otherwise you stand out from other Tor users.
Including it by default is no option unfortunately, due to trademark issues:
And even if we could install it by default, we’d still need a downloader that automates downloading during the build.