Updated 1 April, 2020
Animation Object IDs
The reason is that you can then insert alerts, secondary functions etc. in the triggered function — things you may not anticipate when first setting it up.
The name of a GSAP animation cannot contain a dash, but can contain an underscore.
Adobe Illustrator objects can contain a dash but not an underscore (they’re converted to “_x5F_” when exported).
Except that a dash in the name of a clipping path will break any attempt to animate it.