You are correct. Or as I should have stated it, exponential curves have derivatives in constant proportion to the curve -- so if you look at the change vs the

You are correct. Or as I should have stated it, exponential curves have derivatives in constant proportion to the curve -- so if you look at the change vs the current value, it will be a constant ratio. With a logistic (S) curve, the ratio of the change to the current value will decrease. By the time you get to around 25% of the maximum value, the difference should be visible.