[dice]

I have grown Boxcar Willie a few times, I never saw much catfacing
on the fruit, and I grow in a climate where I see lots of it on larger
fruited, mid-season and later varieties due to cold weather during
fruitset, which can happen any week during the growing season.
(I had an Alacrity plant, a selection from Earliana, where every fruit
was catfaced one year. Good flavor, though.)

What the cold weather during fruitset does is cause pollenation to be
incomplete in the flower. Some ovaries get pollenated and others do
not. The ones that do not end up not developing in the fruit, and it
grows abnormally shaped from the ovaries that did get pollenated.

If you have something else affecting the flowers (like a bug), perhaps
the same thing can happen for reasons other than less than optimal
temperatures during fruitset. A chance mutation that interferes with
fertilization even if there is plenty of pollen there could also cause
catfacing.