Certain UPS jobs are not for everyone.
When you are trained as a preloader in a boxline system, if you are incapable of getting the packages at the back of the cage, they find you something else to do.
I've worked here 21 years in MY building, and they will give preloaders hooks to get items in the back of the cage. I don't speak for other hubs.
Because this is an end-range motion, it can be deemed a safety issue. Your safety committee can work on it.
For a dollar, you can have one made yourself and leave it in one of the trucks you preload. UPS doesn't supply you gloves, but if you want a pair for comfort or safety, you either ask or get some yourself.