2 out of 3 aint bad
Will, I think part of the logic behind the recommendation to replace only 2 of the 3 probes is due to the emerging idea that 3 identical units are more likely to suffer the same problem at the same time than differing units; coupled with the lack of firm hard data characterising the exact nature of icing / blockage at this time.
It is not known as fact whether the BF Goodrich units are impervious to similar issues, so the recommendation allows some additional redundancy in the form of component variation.