I don't buy a graphics engineer would mistake a video file for an actual demo (running a video file at 40 fps is also bizarre, video files are either 24 fps, 30 fps, or rarely 60 fps). The translated version has the engineers clearly saying the SSD throughput only needs to be in the MB/sec range, not GB/sec. Why in the world would you even bother talking about that over a video file. Sweeney likely has a marketing deal with Sony and doesn't want to rock the boat on that. New AMD GPUs getting outperformed by older Nvidia GPUs in actual practise is nothing new, been happening for ages and Epic already admitted the demo will run fine on a 2070 Super. The PS5 is nothing special GPU wise.
There are so many factors that could be at play.
1.) The engineer might have mispoke saying 40 instead of 30.
2.) Sweeney might be respecting some deal.
3.) The PS5 demo might have had some artificial limits set on it, so that it would run at a set standard.
There is so much room for misunderstanding by Sweeney, a technical limit, the engineer mispeaking, or something totally different. It's hard to say.