AD5669R I2C high speed

The datasheet (Rev A, pg 21) says "The AD5629R/AD5669R support standard (100 kHz) and fast (400 kHz) modes. High speed operation is only available on selected models. See the Ordering Guide for a full list of models."
There is nothing on the order guide, or anything else indicating that there is any difference between the parts.
Is there, and if so, what is it?