Yup, that’s new one I haven’t ever seen before. I can see how it could happen.
i do have to note that no matter which way you put that bolt in, there is a large cross groove in the splines that the M10 bolt has to pass through, that locks the splines from slipping out of the yoke. Yes, if its in the wrong way, or is loose, the splines can come loose and there could be play, but I don’t see how that joint could come apart as long as the bolt is still in place through the groove. If the bolt falls out, then yes, it can come apart.
If the splines were not inserted far enough so that the lock bolt can pass IN FRONT of the entire shaft, than that is a real problem, but I think the over all length constraints would make it hard to assemble all the components without realizing something was wrong.
Wish I’d made a list of all the critically wrong stuff I’ve seen on the Datsun’s I’ve touched. Everything from rusted out seat belt mounting points to seats barely bolted down. Trust nothing unless you’ve checked it yourself.