Yeah, I agree that a washer improves the bearing area under the nut, but... I've taken apart a lot of Fender necks where the truss rods have been crushed in and/or snapped off, and in all cases (that I've seen) the crushing mostly happens at the anchor end, the other end. The design of the anchor end of the standard Fender truss rod is the weakest link. It has less surface area pressing against the wood than the nut end, so it crushes first. If the truss rod is really cranked hard, then both ends will crush in.
I don't do Fender neck rebuilds any more, but in years past, I've replaced truss rods in probably a hundred of them. Same general story: Neck has excessive bow; truss rod is crushed in from overtightening; then usually the rod gets snapped. I do remember one neck in particular where the truss rod had pulled so far that it was actually sticking out the heel! It was amazing to me that the neck hadn't split wide open, up around the 1st fret. When I opened it up, I found that the anchor had just pushed the wood aside, squashing it. That particular board must have had a very soft center core.
I sometimes wonder if Leo & Co designed it that way deliberately. It becomes a tell-tale indicator if someone has over torqued the truss rod. Use a depth gauge to measure the depth of the end of the rod in relation to the heel surface, and there's the answer.
By the way, if the rod isn't broken, the crushing can be fixed to some degree. Basically, you tap the rod back into its original depth, then drill a small hole (I think right under the 1st fret?) and inject hard epoxy down into the pocket of crushed wood.
But, of course, that still doesn't solve the real problem, which is that the neck is bowed. That has to be fixed by leveling the frets (in mild cases), using heat to straighten the neck, or pulling the frets and re-machining the fingerboard surface.
I keep bringing this up because this is the main reason why so many necks get damaged or ruined. This is a particular problem with Fender necks, but the same thing happens to modern necks with the new-fangled double rod truss rods. In almost all cases, truss rods get broken because someone overloads it while trying to flatten out a bowed neck. Way beyond a reasonable relief adjustment. If the truss rod is tight, and the neck still has too much relief, then stop right there. The neck is bowed and it needs to be fixed. At that point, fixing the bow usually isn't that big of a job. Releveling or resurfacing. But, if you keep twisting and damage or break the truss rod, then it's a major rebuild. Which, in many cases, will cost more than the neck is worth.
I'm just trying to do my civic duty to prevent the destruction of nice old necks!
