This is a bit exaggerated. Apparently during the crusades knights learned about a training regimen used by arab cavalry involving riding a horse around a pivot and tossing an object between them. The object of the excercise was to train dexterity in battle. European knights inspired, developed games to train their own cavalry. In italian, they called it carusella (little war).

Regular folk thought it was fun, eventually this lead to the development of the children’s carousel. So it’s a stretch to call training tool for death. It was in a very, very different form a training tool for survivability for cavalry.