Desktop APU's have always been about unloading unsold laptop chips. AMD talks a big game about their intentions with their Desktop APU product, but even going back as far as Llano its been about making sure they had a second market for their Laptop dies. They aren't going to reinvent the wheel for a niche of a nice of a niche.I wonder if AMD is trying to use some kind of chiplet style approach to their desktop APUs. They likely don't want to cannibalize sales of their other, higher margin parts if at all possible, and they're strained enough on wafers as is without producing more monolithic chips. I don't think this generation sees that approach, but I don't think it will be too much longer before they go that route.
The piece that's missing is a graphics chiplet. I don't expect them to go that way for their mainstream consumer GPUs consider they said that such an approach resulted in performance scaling issues (no doubt similar to what we saw in the past with SLI/Crossfire), but they did indicate that a chiplet-based approach wasn't an issue for professional use cases, which makes me suspect that the may segment the professional and gaming cards this way in the future.
An APU doesn't need a lot of graphical power and can't make full use of all of its resources in a lot of cases, so that's where it would make sense to pair a CPU chiplet with a GPU chiplet. There's obviously more engineering work to it than simply wishing it so, but the chiplet-based approach already makes good economic sense and it just gives AMD another way to recycle chiplets that might otherwise be defective.