DDR5 gives some performance improvement over DDR5 even at the same speed rating:
https://www.phoronix.com/scan.php?page=article&item=ddr4-ddr5-alderlake&num=2
If the "PC-xxxx" rating was supposed to reflect the actual memory bandwidth in MB/s, where does the DDR5 speedup come from? Maybe lower latency for scattered memory access?