Coy dogs (coyote mom) are not sterile, at all.
Nor are dog-coys (coyote dad). (Dog coys tend to be smaller, probably because the female dog that puts up with a coyote are smaller.)
I’ve dealt with generations of them on the ranch.
OBTW, I learned to be distrustful about the experts when I was very young (in high school). For instance, where I used to hunt deer had rattle snakes. I was talking to a reptile guy from Duke University and he was insistent that rattle snakes did not live where I hunted. I told him that if he did not believe me, I could take him to the hunting camp and I would show him several rattlesnake skins we had mounted on the cabin wall. Besides, rattle snakes are the easiest to ID. He did not take me up on the offer.
In a similar instance, about 20 years ago, a highly regarded expert in Lyme's disease wrote a long article that Lyme's disease did not exist in eastern NC. Which was stupid. Lyme's disease has been in eastern NC since the early 1990s. In 1991 or 1992, Camp Lejeune had the highest incidences of Lyme disease in America (warm winter, so the ticks did not get thinned out, a dry spring so very few controlled burns were performed, and thousands of Marines wandering around the woods every day).