To clarify - I've likely tamed a 3-4 dozen sets of boars to breed at my numerous bases resulting in many hundreds of offspring. The mating pair characteristics and offspring results are very familiar to me. Breeding has nothing to do with my issue.
What I believe happened two times at different locations was that a 1-star boar became a no-star boar during the taming (not breeding) process. Plus boars are not subject to the taming 'despawn' effect of night spawned wolfs to the best of my knowledge.

The 1st time it happened the untamed 1-star boar went into the pen with another untamed but no-star boar, I threw in the taming food, hung around the location doing base-stuff and went to start the breeding process when I got the notification that they were tamed. But the pen just held two no-star boars. These are earth walled pens and clipping weirdness doesn't apply. The first time it happened I thought I had brain farted and, like a politician, "disremembered" the star status'.

The 2nd time it started out the same with a wild 1-star & no-star plus enough taming food to tame both and start the breeding process. I missed the tamed notification but heard the piggy being born and went to see if it came out as a 1-star. Both boars and the piggy were no-stars. This was straightforward transmuting magic unless my brain farting is a chronic condition (DON'T contact my wife to verify this ).

From a game bug viewpoint I can see something getting mixed up when the "wild" boar gets changed into a "tamed" boar. It's not a very big deal but after +3600 game days on my one and only world and taming/breeding enough boars to supply the real world with bacon for a couple of centuries I was curious if anyone else had observed this seemingly rare phenomenon.