Thanks for the clarification... you're right...
I wrote the same code (with different syntax) before... there is a issue when I use set ... it produces a jerking initial movement...
I modified your code to :
const tl = new TimelineMax({repeat: -1, yoyo: true});
tl
.to(e, 1, { x: -5})
.to(e, 1, {ease: Power1.easeInOut, x: 5})
With this one we haven't that jerking initial movement but the animation distortion between iteration occur...
You're not the only ones who confused now