Hi Stu, I am no expert with hogs, but been doing this stuff a long time. While hogs are without question, very dimorphic where gender is concerned, there are tweeners.

When I determine gender, I use all methods, not one, to evert, to probe and visually(scale count, tail length,etc) With all snakes, I like them to harden up first, usually a few days after the first shed. I am not sure how well probing will work with hatchling tweener hogs, as when everted, they have tiny tiny tiny hemipenes. So I imagine they will not probe too deeply either.

This is a common problem with varanids, most are physically female when they hatch, and males change from that in a matter of days, months or many months later. Turtles do that as well.

They grow out of this tweener stage pretty quick, a matter of a few weeks to a month or two.

This year, I collected a hatchling axanthic, that was a tweener, and I really wanted a male, it is growing out to be a male.