Findo
Theres a difference between a clearance and a restriction.
A clearance is not changed by adding a restriction, so by telling a pilot to cross XYZ FL100 does not change his clearance to FL160.
Similarly a route clearance Flight planned route to destination is not altered by a DCT, all this does is puts the a/c on his FPR at a later stage whereby he will continue as per his route clearance.
I do agree though there is no rule book to cover all possible scenarios, which brings us back to the old mantra
If in doubt.........ask!!