Nope. It further reduces the strength of the shaft, and increases the amount of stress risers. Now why would they still do it? View attachment 1716310139
As I read that, the line that says "in case the key way is too long..." kindda sums up my point and even elaborates that long continuous keyways contribute to shaft twist. A long keyway cut for single sliding key is pretty detrimental strength wise, where multiple half moon key slots is a much more rigid and robust setup.
That said, I'm not a crank engineer, and if you know some other reason, share it. As I said, keys aren't designed to carry loads and the furthest I 'officially' opined on.
You're welcome to slather your crank and cam bolts in red thread locker and leave them finger tight if you want to prove to me that the key carries the load.