DDR5 uses on-die ECC to improve chip yield (AFAIK.) Any errors are not reported to the OS so the BSODs you experience are not resulting from reported ECC errors

DDR5 uses on-die ECC to improve chip yield (AFAIK.) Any errors are not reported to the OS so the BSODs you experience are not resulting from reported ECC errors. They could be the result of uncorrected memory errors that are undetected but cause the OS to crash. Some DDR4 also uses on-die ECC. The specs for the Raspberry Pi 4B list DDR4 ECC RAM.