So what you mean is that it doesn't matter what the amplification (RFU) or the Ct value is if there are two curves then it is heterozygous regardless of the intensities.
Let say orange represents allele 1 and blue repersents allele 2. On the amplification plot (where you see curves) there are both orange and blue curves but with there two examples:
1: Orange and blue are on top of each other meaning a very clear heterozygote and no difference or space between the two curves, the Ct and RFU's are exactly the same
2: The orange curve is at top and the blue curve just above the threshold, meaning the difference between the two curve are huge
Is number two also a heterozygote
Example pictures of number 1 and 2
1.bmp
2.bmp