A guess as to why:
It's becoming a marginally small cup and ball for the approx 900-1000 lbs of peak pressure on them (and even much higher peak loads dynamically at high RPM's). The psi on the oil film in that small area gets pretty high, and a hole within that small contact area takes away even more of that contact area, which results in the oil film being penetrated. In that regard, the hole in the pushrod IS a path for the oil to escape from the cup, so in that sense, the oil would flow 'backwards'.
Either no hole or a larger pushrod/cup reduces the psi on the oil film.
At least they were sharp enough to ask about your spring pressures and connect it with past problems.
