I have exactly the same HW (but the 2TB nvme model) and am facing the same issue as you described. FW customer support advised me to do a “mainboard reset” as described here [1].
After resetting the mainboard i had a run for about a whole month with the machine not resetting itself after resume from suspend a single time (usually it takes about 3-6 suspend cycles to trigger the issue here).
A few days ago, it appears my lucky streak came to an, considering the issue, truly abrupt end and the issue started happening again.
I have had this issue since i received the laptop to this day, have tried a lot of different things, and so far, nothing appears to have solved the issue, unfortunately.
You mentioned that the kernel may still have “that platform quirk: setting simple suspend” issue”, and haven’t come across this one.
Have you tried running the system with the “amd-pmf”-module blacklisted as mentioned here [2]?
[1] Reset forgotten BIOS password - #17 by sgilderd
[2] 6.8-rc: system freezes after resuming from suspend