No, I wasn't aware of that. How did they build for the PS5, when they didn't even know what specs or architecture of PS5 would be? Did Sony let them in on it early or something?
PD build it from the ground up to support native 8K, 120 fps, 10 bit rec.2020 up to 10K nits, from source textures all the way to the end result. It's made ready for ray tracing, yet since the ps4 doesn't have that it was using pre-rendered lighting, shadows and reflections instead.
The precise specs don't matter when building a new engine. Making sure you can support all the expected features (rec.2020, HDR, ray tracing) to their fullest extent is what makes it future proof. The SSD speed is a nice bonus, but likely won't be fully utilized to stream data beyond faster loading.
Now GTPlanet has revealed that Gran Turismo Sport was recently showcased at a Japanese consumer electronics show in Tokyo dubbed ‘InterBEE 2018.’ Sony was there to showcase its high-end Crystal LED displays, with a massive 440-inch screen displaying Gran Turismo Sport in native 8K resolution at a blistering 120fps.