Or they do something similar like Intel recently did: Advertise some magic to use both the integrated graphics and the discrete graphics, but in the end it was

Or they do something similar like Intel recently did: Advertise some magic to use both the integrated graphics and the discrete graphics, but in the end it was just a more or less straight forward distribution of workloads over multiple GPU's without any "hardware" magic. And IMHO that probably is good enough for most use cases if done well, as many common tasks can be split surprisingly well e.g. run desktop and application GUI as well as fast hardware accelerated (already existing) video decoder on iGPU but place the video encoding and complex computations on the discrete GPU or similar.