From a timing-closure point of view, reducing from 4C to 2C would be a heck of a lot easier than expanding from 4C to 8C. They probably wouldn't be looking to enhance any latencies in the process, just maintain the status quo.
I would also speculate that they'd reduce the PCIe lane count (similar to current APUs), use a single-channel IMC, drop all of the MCM support features, and use a considerably smaller iGPU than Raven Ridge to match.
This would result in not only a much smaller and cheaper die, but also a significantly lower system cost due to the fewer board traces and sockets required to complete the system. This therefore addresses a much lower-cost and higher-volume segment of the market than either Summit Ridge or Raven Ridge can, even with harvesting. That segment would otherwise be left to Stoney Ridge (using obsolete Excavator cores and Fiji-derived iGPU on equally obsolete 28nm process), or even to Intel (heaven forbid).
Of course, by reducing production costs, a decent profit margin can still be maintained that, with high volume sales, contributes materially to the bottom line.