There is a lot of confusion in the flat tappet scene because once FT's went out the window and were replaced by roller sticks the quality went downhill rapidly. Heck, GM had quite a period even when they were popular where the lobes were improperly hardened and you were bound to lose some, and that's on a very mild OE broomstick cam.I mean you did have 130,000 miles on it already. Don't most high performances engines (BMW) **** the bed at like 70k? Lol. I don't think this was a gradual wear issue. Seems like it happened overnight. I have a vintage car and peruse the forums. They say you have to at least put high zinc oil in after a rebuild until the engine breaks in. So after a cam swap for example.
So, people started blaming the reduction in ZDDP, dumping wizards in their oil...etc all kinds of stuff. The reality is that "back in the day" oils didn't have insanely high ZDDP levels like many like to think they did. Yes, with the introduction of API SM, phosphorous was restricted, however, oils that it was not restricted on, like the Euro oils that don't care about the API approval, don't have 1,400ppm of phosphorous, they have around 1,000-1,100ppm, even though it could be much, MUCH higher if the blenders wanted.
Several years back now, a buddy of mine and I did some upgrades on an SBC of his dad's. One of those upgrades was the fitment of a very wild profiled Lunati Voodoo camshaft, which had ramps that were much more aggressive than what you'd normally see with an FT stick. We used lots of assembly lube and broke it in per the instructions, using Kendall 15W-40, which is what was run in it (think there was some Esso 15W-40 used at some point there too) for several years until we put together a new roller motor for it (and upgraded it to fuel injection). When that very aggressive stick was pulled, the cam and lifters looked fantastic, despite never seeing anything other than some inexpensive diesel oil.
Formulation is a balancing act and I think it's quite telling that in applications like full-SAPS Euro oils where phosphorous isn't restricted, they aren't shooting for the moon. Many of these applications are cam-over-bucket (sliding follower) which makes them very similar to the OP's. Some of them, like Mercedes AMG, Porsche, BMW M, have pretty aggressive camshaft profiles too and the approvals have strict wear limits.