Isn't a belt loop also ambidextrous ?
I can see the scout carry just getting caught up on stuff or being really uncomfortable if you sit down or drive.
AS an ambidextrous person I generally hang a knife sheath on whichever side of my belt has space
My gerber usually rides on my left, so knives tend to go on the right.
But I've had them on the left before.
Never noticed any side specific issues with a vertical pouch.
It also looks like if the catch comes loose, a knife could easily fall out of a horizontal scabbard - particularly if you were hiking or climbing or going through any kind of brush.