What you are saying is that from now on if you fly multi segments they ALL have to clear and be available as the original route? Did you ever experience that in ANY airlines including TK?
That's actually happened to me on TK. I had a flight AAA-BBB-CCC booked in K, which allowed changes. I wanted to change the AAA-BBB segment; there was availability in K on the new flight; but there was no longer availability in K on the BBB-CCC segment (which I did NOT want to change!) They couldn't do it.
Shuly