All I can think is that it’s a new decompression algo, the compression would stay the same but the decompression would improve. The files themselves wouldn’t need to change. It’s a bit weird though and also that they’ve chosen to release it now. Maybe when they ported games to the PS5 they found the load times didn’t improve with the SSD like they thought because the decompression was so inefficient.
Also very likely GoT has been using this already, the load times on that are crazy fast.