Highs aren't meant to hit crouching opponents and the only reason some high attacks hit crouching opponents is because the characters collision box is lowered by the size of the character.
Only mids, lows, and overheads are meant to hit crouching opponents.
You'll never understand why the design choice of how a character plays unless you work for nrs.
When i first started playing Shao on released i questioned how he played because he seemed incomplete compared to other characters.
I felt similar feeling with Laura when sfv was released as she felt incomplete.
That's the devs decision based on how they want to make the characters in the game.
You either accept how they play or play someone else or choose to complain about something you don't agree with and hope the devs listen and change what you don't agree with.