The area savings for shaving off that portion of the FPU seem minor in the grand scheme of things. Would the bright areas on either side of the CPU section be test silicon/pads, or could those areas be blank? There are some sort of visible striations, but I don't recognize the patterns from other AMD silicon.
Would Sony have been that desperate for die area to pay for a rearchitecting of the FPU and new layout, or maybe this is something AMD had on offer, like a scrapped alternate version of the mobile core?
Another consideration is thermal density, since Microsoft cites the 256-bit FPU as being the thermal limiter of the Series X.
https://www.anandtech.com/show/16489/xbox-series-x-soc-power-thermal-and-yield-tradeoffs
"For Scarlett, it is actually the CPU that becomes the limiting factor. Using AMD’s high-performance x86 Zen 2 cores, rather than the low power Jaguar cores from the previous generation, combined with how gaming workloads have evolved in the 7 years since, means that when a gaming workload starts to ramp up, the dual 256-bit floating point units on the CPU is where the highest thermal density point happens."
Granted, the PS5 GPU probably ramps thermal density significantly more, and then there's the liquid metal TIM.
Individuals expecting Zen3 were setting themselves up for disappointment. I don't consider that a fair standard to measure the downgrade.
From the die shot, the GPU really dominates the die area already. The ratio of GPU to overall die area may need to checked with the PS4 and PS4 Pro. This might be somewhere in the same range as the original PS4, while the GPU area for the PS4 Pro was even more lopsided.
36 would make sense as a minimum that they couldn't go below.
The clocking method isn't particularly new, as far as AMD is concerned. The PS5 implements a less aggressive version of AMD's DVFS.
The claim that the CPU supports native 256-bt instructions leads to questions about what was done the FPU.
The register file is split like the original 256-bit Zen 2 FPU, but the area and layout don't match very well. If the FPU were treated like two 64-bit halves, that might explain why the alleged register file section is also narrower.
The Bulldozer line did have a series of changes to the FPU, first by dropping one FP pipe, and then the Steamroller to Excavator transition included high-density libraries that saved quite a bit of area at the expense of top-line clocks. The area savings were notable for the FPU, but I don't think they were limited to just the FP portion and the register file didn't benefit that much.
The PS5's CPU cores look pretty standard outside of the FPU.
RDNA GPUs have gone with either layout, depending on unit counts and possibly considerations like making room for other silicon.
Using a two-sided arrangement like the PS4 Pro means that particular way of growing the GPU in a mid-gen refresh is ruled out.