You might have been thinking about XCGPU that were part of the die shrink in Vejle and Oban. Those were in the 360 S and E models.My bad on 360. I only remembered the name Xenos and forgot about Xenon. Yep. Two separate packages.
While that did merge the CPU and GPU dies on a single package. Their design was set to simulate the exact same latencies from the two chip design.
APU is a made up term from AMD which has the CPU and GPU existing within the same die. Not just being an SoC on the same package.
https://xenonlibrary.com/wiki/XCGPU