I have two listeroids (twin & single) both engines have these holes. My two nearby listeroid owning friends each engine has them too. What I found is you can twist the base around so the holes face forwards, sideways, or backwards with respect to the rotation of the crankshaft. I've found or at least I preceive this allows you to introduce a little more oil splash into the angle drilled hole which provides more or less life sustaining oil to the rotating taplet. Personnally, I really like this feature, easy to adjust with a pipe wrench to twist the taplet guide around 90 or 180 degrees to evaluate the difference.
Also, each of us polished all the burrs off of the taplet shaft, cleaned up the spiral groove which was a mess. The results has been spinning taplets that function perfectly and get good lubrication. You got love these brutally simple machines.