OCR with VNRecognizeTextRequest

Using VNRecognizeTextRequest from Vision framework, I’m not able to make it recognise characters from shortcuts: the string “⌘⌥⇧⌃U” will return “8T0^U”.

I’ve set the language to “en_US_POSIX” but it’s useless.
I also tried to set customWords to (characters of "⌘⌥⇧⌃↩⌤⇤⇥⌦⌫⎋↖↘⇞⇟⇡⇣⇠⇢␣⌧⏏") with no success.

Is there any way to acheive this?