More like a full (transportation) truck driver helper, since a loader could be one of team of hands hired to load delivery trucks, etc. And working by shifts.
As per some descriptions I saw on the Web.
Anyway, one can think of such helper is a loader too. Indeed in Brazil those are more of a loader than driver helper.
Only a tiny fraction of them has a driver licence and when they get a licence they become truck drivers, as if that was a promotion of sorts.
But again, a tiny fraction, a lucky selected few indeed!