WSP contains a TermSet but it isn't imported

We've exported a Site Collection which contains Term Set navigation as a WSP.

Opening the WSP as a Cab I can see that it contains the TermSet

However, whether I use Powershell to deploy the WSP at a Web Application level the GUI to deploy it at Farm level, the actual Term Set is not imported.

I see there are lots of tools around to manually export/import term sets, but I would have thought that if the WSP contains the Terms then SharePoint would bring them through - it's like Microsoft only got as far as writing the export bit and never wrote the import routines?

Any suggestions please of a way that doesn't require us to manually recreate and reattach all the terms (or rewrite the one of the powershells that are out there for 2010). It'd be ideal to use a Microsoft way of doing it.