The 70-floor design had its true rooftop, not counting roof elements, at just above the height of Scotia Plaza at 275m. That would give an average floor height of about 3.94m, which is typical of modern 'luxury' residential highrises.
If the height remained the same, but with 57 floors, the floor height becomes 4.84m, which is definitely at the top of the range, although it is seen in Dubai.
If the floor height remains 3.94m with 57 floors, the true rooftop becomes 225m -- losing 50m in height. If the rooftop elements remain the same, this gives a total height to the tip of the spire of about 275m, the same as Scotia Plaza.
It is also possible that the floor height will increase, but not enough to avoid a decrease in rooftop height.
My own guess would be that the rooftop height remains about the same, at 275m, but with a greater floor height.
Bill