Small block Fords, i.e., 260, 289, 302, 351w that use the rail type rocker arm system and the cast rocker arms show more wear on the valve train than do the Clevelands but they have their issues also.
In MY experience with those engines, worn components such as the valve stem and rocker arm tips also indicate wear to the lifter surface and the camshaft lobe.
Along with the push rod they are oiled as an assembly.
As the tips wear, oil pressure to those components are reduced.
The camshaft lobe has the largest contact area along with the lifter. With less oiling it will show greater wear.
Multi-viscosity oils start breaking down immediately. Visosity such as 10w-30 or whatever is only that brand new inside the container.
As soon as you use it the viscosity polymers begin to break down.
By 3,000 miles, your 10-30 is now a 5-5 or somewhere around that.
The valve train is the most demading on viscosity. The bearings don't care as much.
I saw this on a friends Pro-stock BB Chevy. It would have 100 psi at the starting line and when it would come back to the pits, 10 psi.
Granted there were other things happening internally, but 95% of that was that the viscosity of the oil just got destroyed...AND it wasn't mult-grade either!
I constantly do oil changes on cars with more than 7,000 miles on the oil. Constantly is a good description. New vehicles too. Many on leases and the owners don't care.
Wear like this IS oiling related. Is it wear and tear? Yes, but wear and tear caused by insufficient oiling properties.
Incidentally, you want to use maximum ZDDT, not a minimal amount like many of these oils offer.
When you drain the oil from the pan, you clearly see the ZDDT floating on the top of the oil like an oil slick.
It is a whiteish/greyish slick floating on top of the oil.
On those SB Fords, I have had to replace entire valve trains on engines with as little as about 75,000 miles.
I always advise that in addition to the accessable top end parts I am changing, that the cam should be changed and the valve guides are probably elongated too and should be redone.
I advise putting in roller rocker arms probably more than most, and when the price is mentioned, probably install the least.
There's more to it than just not enough ZDDT.