This is pretty typical for game development, especially for games that are dealing with new technology. There's an optimization curve they go through that improves performance and thus the quality of the final product can push. It's actually games like Ratchet and Clank that makes me want to get a PS5 despite primarily being a PC gamer.
It's a good example of one of the benefits of fixed hardware in the consoles, being that you can optimize games much more for that one tightly constrained configuration, rather than being stuck with a plethora of PC hardware and the various different settings you need to offer. Still many of these "optimizations" tend to be about low hanging fruit or artistic trade off. So maybe one scene is heavy on RT reflections but they can dial back on RT shadows or any kind of global illumination. And another level or area can use some nice shadows in a stylistic showcase of dynamic lights but have no reflective surfaces nearby. So you can spend your limit RT budget in different ways at different times to have the maximum visual impact. There's much more room for artistic flare.
Where as with a PC game you can just slap reflective surfaces on whatever you like, have dynamic shadows and GI and do all that stuff at once and do it everywhere and leave it up to the gamer to decide what they'll enable or disable in the settings to get the performance they want. Ideally you'd like it all if you've got the power to do it. It's why RT features are suspiciously missing in areas in that video, like the green swamp water using traditional screen space reflections. You spend your relatively minor RT budget on whatever has the maximum visual impact at the time.
There's a lot of the same tricks being used here however, the RT 60fps mode has a nice frame rate but the quality mode is at 30fps which suggests they're skimping on a lot of settings between the 2 modes, dynamic resolution is there which is unsurprisingly so you can just dump down the res in real time if the APU is struggling. But for basically budget gaming setup with very lite RT capability it's actually very impressive. And what's more impressive is DF's really deep dive on these kind of videos. If you're not subbed to them you ought to be.
