I would believe it allowed Khan access to get the transwarp beaming device.
...But he only needed that device to get to the Klingon homeworld. Which is where Admiral Marcus wanted him to go, because that would get the war started. How was Marcus planning on getting him to that planet if the Admiral himself didn't provide this gadget?
It's an interesting little waltz there, and one never knows which one of the villains is leading - Khan or Marcus. Both have some goals in common - getting Federation and Starfleet assets blown to pieces for
casus belli, getting Khan to Klingon space, getting Kirk and his torpedo/Augment-laden ship to Klingon space. Both have opposite goals, too, not the least of these being they want each other dead.
The bit where Khan gets the transwarp ghetto-blaster is among the unclear ones. Who planned this? Did everything go according to that plan? And would Harewood have approved of that plan? Say, Khan comes to him and says "In exchange for your daughter's life, blow up this place - it's being used to ignite a horrible war, and even I can't kill the monstrous Admiral behind it all, but you can destroy his weapons shop", or Marcus sends Khan to say "In exchange for your daughter's life, blow up this place - this will ignite a horrible war which we will win and Klingons won't rape your daughter after all"...
Timo Saloniemi