This is more or less an carefully optimized port. I would also guess, that it uses the same packaging as PC and no decompression via hardware just brute-force CPU usage. They are a small team and according to their games legacy, they don't have the necessary knowledge/manpower to optimize a game for every platform. Using RT in that title was just overkill without further optimization. RT is always expensive, even if it is not visible in every scene. We've seen this in Battlefield 5 where there was absolut no reflection in some levels, but the performance was still much worse than without RT. And Dice has the manpower and knowledge to optimize for something like this.imo good decision by Bloober to chose higher res over rt, rt was subtle on xsx and resolution drop even under 900p, no need to have even bigger res drops on ps5 (tough loading times show that Bloober is not a master of ps5 utilization )
I guess smaller teams, will start to implement RT in their games, once it is not much more than a flag in the engine and already runs well optimized. Their might be exceptions but all in all it is currently much more work than the traditional way (that must also get implemented).