These Oldie Tracks Are Strange

Those odd 'short' pieces you mention look as though they are wedge shapped (i.e. the non keyed end is thinner. I suspect that the idea is you would fit them to one of the 'Y' ends (i.e. the forks) and use it as a rolling loader for your trains. If you check out the special Advance track set that was released a year or so back you will see it has exactly the same feature. A specialised set of points with a sloped dead-end to allow you to roll the train onto it, turn it on and let it load itself onto the rails rather than fiddle around trying to seat it correctly.