Right, but IIRC, the OS runs as a single processor OS, and the second CPU is treated as more like a peripheral. You write your video / graphics processing code for the second ARM and then it becomes an application specific accelerator, not too much different than dedicated hardware, but tuned for a particular app.
Heck, even desktop PCs have been asymmetric multiprocessor since their introduction (8038 in the keyboard controller, 8088 running the apps), but the OS really only thinks about the main CPU.
The A7/A15 split is rather different: This wants to run SMP Linux across both types of cores, dynamically moving tasks between the A7 and A15 side of the world seamlessly. All of the processor cores are considered generic resources, just with different performance/power envelopes. That's rather different from the GP2X model.