I was thinking about this today, and although grinding down the "burr" may let more oil out of the shaft it may still not get up to the vent hole.
If you add the height of the "burr" plus shaft wear, the top of the shaft will be that far from the top of the rocker shaft bore.
There is likely to be quite a gap for any oil to jump. Most of the oil will likely leak out the sides of the rockers before reaching the vent hole.


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