Of all the NIANA items, this is one I least understand... I think most every Festool woodworker in NA would have some of these extrusions in their shop. I have a MFT/3 and want these so I can make some custom table supports... provide Festool clamping options on my non-Kapex chop saw... tons of other ideas.
The profiles allow you to use the Festool guide rail and fence fittings if you don't want to use dogs for the guide rail and 80/20 extrusions for the fence alignment.
If you use Parf Dogs or Qwas dogs for the rail and other compatible dogs or 80/20 for a fence. you won't need the Festool profiles.