When we wind wool of any kind to crochet, we must make the ball with slack. To achieve it you must do around the fingers. Thus, bringing them out, the ball will have the necessary slack.
The material stretches when we make hard skeins as balls. And this can affect when we weave our work, leaving some uneven sections and therefore look ugly.
If we wind with winder we must ensure do with slackness.
Do not forget this detail often not taken into account when we are beginners.