years ago they would block a tail in western pleasure horses, actually a block under the tail , and a whack . it prevented the horse from lifting its tail high. For breeds with a high tail set, the opposite would be done and set it always be raised.
The fake tails to me are like hair extensions in people. It is not permanant and it does not injure the horse unlike, the tail blocking, and the soring etc that is done.injecting tails for pleasure horses is done all of the time. Fake tails would also fall under this I believe. Cosmetic devices are most certainly used. Overlong toes and high heels are used in some breeds to exaggerate gait.