We were taught in grade school that the vowels were "A, E, I, O, U....and sometimes Y" without any real explanation. I count that as our first lesson about the convoluted complexities of the English language.
Not a hard rule, honestly.
Some Indian languages exhibit a blurring of sorts with Ye- sounds. E.g., in Telugu, the word for 'How' is 'yela', which is often also pronounced as 'ela'. TBF, Telugu also blurs Ve-/We- sounds similarly.
The word "eye" is an interesting one. It seems to be only vowels, based on pronunciation.
I dare say its made up as it goes along