It was advertised as a 73. Confirmed the measurements for a 73 spindle. Has me at a loss as to what could chew a groove that deep. If it can't be seen, there is a deep lip on both sides.
That has to be an inner wheel bearing failure. The seal rides further back on the shoulder, and the inner race should be seated against the lower section of that. That looks like where the roller for the wheel bearing would be, so maybe a roller backed out of the cage?
Still problematic, you're definitely going to need to dress that rough spot out, and then check and make sure that groove doesn't interfere with the location of the inner race for the wheel bearing.