Perhaps I am mistaken.
Shin, Kaph, Nun
I’m not getting what you mean.
“Shin, Kaph, Nun” where?
The pronunciation marks define where and what the vowels are.
Yahwey is improper because a vowel sound is missing. It also has no correspondence anywhere in scripture. For example, if yahwey were a name, the short form would be “yey,” not Yah. It’s gibberish that way.