World height altering data pack does not generate above y=0

i was messing around with world height settings and world gen to use upto -256 y

and the top of y 0 is air over wise i left world gen un touched  i dont know is there some i did wrong i have included the data pack 1.17 data i made it myself turns out no matter what you put for max height it resorts to 0 cutting the world to 256 form y 0