Knight at Arms
Body parts remain visible beyond the shield even with the directional shield blocking - all the more so, when it's in any position but down, and even then the feet aren't covered (physically). Meanwhile, if you direct the shield up to protect your face while looking straight forward (at least as a Varyag), it does this...There is directional shield blocking in the game, if it was only made smoother one could block the incoming arrow by changing position of the shield. Getting hit by an srrow shouldn't be fatal anyway wearing metal armor. You realistically should only have to worry about your face when it comes to arrows unless you're dressed in cloth or leather.
Even if the arrow doesn't kill you, it still feels incredibly annoying to get shot past the shield, and you can't always be playing in heavy armour. It's also too much to expect infantry to quickly direct the shield to cover whichever body part the archer will suddenly be aiming towards.
In Warband, it could be really quick shielding an arrow in the heat of battle:
In Bannerlord, this happens:
I guess I could have tried to look at the archer at a 45 degree angle while holding the shield to the left, but ... it's not exactly feeling intuitive.