Mr Feet, You can tell your youngster that his Friday fact is a Friday falsehood 🙂
There’s no special exemption for vets.
Anybody can provide medical treatment for humans in the UK so long as they don’t prescribe, don’t sign certain statutory forms, don’t falsely represent themselves as qualified doctors of medicine and don’t falsely claim to be licensed.
Can Doctors treat animals?
The Royal College of Veterinary Surgeons says
Only registered members of the Royal College of Veterinary Surgeons may practise veterinary surgery. …
A number of exceptions apply …
anyone administering emergency first aid to save life or relieve pain or suffering
Overall conclusion
Anyone, including Doctors, can treat animals in emergencies (subject to important provisos)
Anyone, including Vets, can treat humans (with some important restrictions)