It's not as cut dry. The explanation is exactly as I suspected!
When ps5 came out, I tried Demons Souls in 30fps but it was VERY laggy and slow to control... and I like 30fps.
I brushed it off, switched to 60fps and finished the game. But on ng+ I tested a bit and reinstalled BB on ps5.
And BB indeed controls much more responsive than DeS at 30fps. It's snappy and does not have that that delayed feel.
I also recently replayed UC4 4k30 remaster mode and it's also better than DeS at 30.
Turns out I was right! From are "geniuses" and the frame pacing is a visual cost for saving like 70ms of input lag! John even talks about it at the end of the video.
This explains everything.
The frame pacing itself never bothered me that much. It's really not noticeable if you enjoy the game and do not look for it.
TBH, jaggies in BB are more annoying than framepacing. I am sure 4k60 port is coming... right ?!