I’ve followed your steps but changed it to a traditional sideways book. The pages flip from right to left.
Where you had ‘X’ I changed to “Y”. This all worked perfectly until step 9.
“9) Keyframed Warp Direction starting with 90 then to 150 about 25% into fold then back to 90 at end”
After I did that the left side flipped properly but it was the right side that curled.
Could you please tell me in the same style as your steps what I should enter to make the left side (the side that flips) curl.