Yes but that's an interface problem.

Ofcourse you can't provide more decimals than the number of bits used by the float.

EDIT:

  0.999 * 255 (8 bit) = 255
  0.9999 * 255 (8 bit) = 255
  0.999 * 4096 (12 bit) = 4092
  0.9999 * 4096 (12 bit) = 4096

So for lower color depths the number of decimals isn't that important.