Consider first an animal with a two toed hoof such as cow or goat. Where do we put the ting points.? The hoof is balanced inside and outside not front and back.(lateral and medial)
In 1974 when the present commonly used format for t ting points was adopted by the IVAS there was very little knowledge of acupuncture on the West and no understanding whatsoever of Yin/Yang. It was a vague theory then and for most veterinaraians even now remains a vague theory. Something Oriental and not scientific.
The Transpositional System.
They worked out their naming of the Ting points by assuming ( and this is a big assumption) a transposition could occur between humans and animals especially horses. They used comparative anatomy, which indicates that the one digit of the horse corresponds to the third or middle digit on the human.. So the Triple heater point is in the middle front and others around it. This will work in practice on horses because of the power of the ting points to cover a broad area. But its not Yin/Yang correct. In some theories the hand was 'scrunched' up to look like a hoof.
Yin and Yang
My background is from Acupuncture. I completed my acupuncture degree in 1980. I also worked out a transpositional system but based on Yin and Yang..
Yang is the protective energy and external and Yin is the nourishing energy and internal.
On the foreleg the outside(lateral) is the protective part not the front. And in the hind leg there is no need for protection on the fore part of the leg where the anatomical transpositional system puts it.
So the original assumption has to be modified.
Unfortunately the veterinary anatomical transpositional system will persist. It reminds me of the fact that Native Americans are still called Indians because when Columbus first found them he thought he was in India. No-one questions it anymore . But its obviously incorrect.
Yang at back - Yin at front