Didn't make any sense to me at first, either, but there have been far too many complaints about Home that were resolved by the installation of .net to ignore. One wonders if some support file, rather than the core of .net itself, is at the heart of it.
My guess is similar: that by going through Windows Update and installing something major like .NET, the system is forced to (re)register several DLLs, repair several parts of the registry etc - which all, in turn, improve the stability and functionality of the computer, hence TT's application behaving normally (as in TT's "normal" - I also use it on a Unix machine - OS X, in fact, and there are a lot of Javascript errors in the logs, each and every time I'm using it - errors that are not being logged in Windows, as the logging system there is less thorough).
Anyway: sloppy work, TomTom. But... what's new here?