As someone that does both, no it is not quackery. I went through school to be a DC and then decided I wanted to be a Vet. Ended up getting through school and then getting certified in all aspect of animal chiropractic. I use it all the time and it works.
That guy I don't know anything about other than what I have seen of him in tiktok. Several countries have no laws regarding treatment of animals with regards to chiropractic.