Ummmm…, you know this is not new. Thumbgen has worked with the HUB and SMP for a long time. Your a little late just now discovering this.
But, to make it work so that moviesheets show up correctly, you should really be using a theme that is designed to work with moviesheets. The default theme is not setup to use moviesheets (at least none that are avaiable) and if you use the default moviesheet it will not display correctly, due to the moviesheet containing the metadata, but the metadata is also displayed using the xml data so you will have double text.
Also, you can find info on how to setup Thumbgen for the SMP/HUB, HERE. This is for my theme, but the setup is pretty much the same for any Moviesheet theme with a few minor difference.
And I don’t recommend running TG in automatic mode the first time you generate data for you files, as you never know what you’ll get (like having foreign coverart). It’s best to run it in Manual mode so you can select exactly what you want TG to generate.
Another thing, xml data for TV Shows doesn’t work correctly and the format for TV xml’s are different than it is for Movies, so you will have to manually edit the xml data created by TG. However, TG is aware of this and hopefully by the next release this will be fixed.