jan Misali (or possibly others, but this is the first known occurrence to my knowledge) has argued that a much better example would be pfysche [1], which is within the observed English spelling rules and still hard to predict its pronunciation.
As a non native speaker I had a hard time with "scythe" which as far as I can tell is not matching all the rules in this page, and at the same time is relatively common.
I think rule 12 covers the vowel, and then rule 20 explains why it's sï+ not skï+ but I could be wrong about whether the vowel is a front vowel or not.