The angle is not some drastic to the eye type of deal. It is what caused the roadranger I fixed to have to be held in gear by the driver. I was much younger then and had talked to an old time truck gear shop guy that sold us the parts that he knew by hearing the symtoms would need replacing, hes the one that said that was going to be the problem. And not the last time I've seen the problem on manual transmissions. Torque load causes axial pressure to force the splines out of engagement when an ever so slight angle is worn into the surface of the shift splines, it takes lots of years of loading to do it, along with some metal in the oil.
