Re: Crinrict, on the owned horse: Looked like it wasn't the wild horse, because the wild horse that looked like that showed up. And, it was definitely owned because I could "request permission to ride." I could also "lead" it, which you can't do with a wild horse (even though there used to be wishes that would appear relating to leading or riding a wild horse, when you couldn't!).
Edit to add: As to the not being able to pet horses, I noticed when I went in to take out any cc related to horses from my main game folder, I had some sliders that affect pets. They never caused any problems with interactions before, but I wonder if the update did something? Regardless, am taking them out to hopefully test that.