In today's "modern" engines, a key simply locates and is not intended to carry any shear loads. The bolt stretch provides clamp load which creates a joint held in place by friction.
I wouldn't know what our forefathers designed "back in the day" on these old engines. I doubt they used the key to carry shear but I wasn't there (I'm old but not that old!).
I have used offset keys in the past to get a cam degreed where I wanted it. Sometimes an offset key and a tooth off in the other direction - whatever it took to get the proper centerline. I've never had any issues with offset keys but IIRC the most I used was a 4 degree key. FWIW.