Why The Bullet Truss-rod?

It is difficult to adjust the truss rod from the heel without removing the neck. Maybe with the earlier design, Fender assumed they could preset the neck at the factory as the variety of string types/gauges were very limited so user adjustment was considered unnecessary. As more string types and gauges became available the need to facilitate easier user adjustment arose, and headstock adjustment was the an easier solution than re-jigging for additional body routes. YMMV

 

I'm not sure why Fender put the bullet nose on the truss rod nuts. It could be because of the process they used to make the hex socket on the end. They may have crimped the steel around a hex arbor, which would leave the OD rough. So, they turned the excess metal into the bullet shape to clean it up. These days, hex sockets are cut by a process called Rotary Broaching. But, back in the '60's, I don't think rotary broaching was in much use in machine shops.

When a Fender truss rod starts lifting up the inlay or the fingerboard, that's the square washer on the end of the rod doing the lifting. When you overtighten the Fender Truss rod, the wood behind the washer starts crushing. And it usually starts smashing unevenly, tilting the washer at an angle. Then the washer starts slipping upwards and pushes up against the underside of the fingerboard. Keep tightening it, and it will push up the inlay or a section of the fingerboard.