I have a similar sleeve since we have roller furling and more than one sail without built in sun cover it made sense. It will protect the sail better than a sun screen against polluted air.
The compression strings stops the cover from flapping and moving.
We have a small bag we can tie on to the pulpit while hoisting or taking down easier to stow than a long length of canvass.
This video show how easy it is, note that there was some wind..