you can bring anything in, when it is properly wrapped in your suitcase (no broblem), as long as you do not carry it in your hands, as a duty free item from the previous airport.

In the case of Doha airport, the explanation is "Money talks", anything that generate new "money(s)", authorities like it a lot. Bringing pork or a duty free bottle from another airport, does that generate money for the state? Noooo! Hence it's banned; simple.

QDC, does it generate money? Hotels and beer drinking holes around town, do they generate money for the state? They sure do! So they are all OK :D