I've seen this happen on extremely rare occasions when a factory block has a big, deep chamfer at the top of the lifter bore. I use mainly Morel lifters and just don't see many issues on a large sample size.
I really wish I could get everyone in the habit of priming the oil pump with the intake manifold off, just to see where the oil is going. 95% of issues would be caught, but lots of guys like to put the entire engine together, stick it in the car, then prime the pump.