From the poster's terminology they're USA based, in which case it's not just an endorsement.
USA uses a system of discreet, complete-within-themself licences covering every combination of single/multi/landplane/seaplane/fixed wing/rotary wing/private/commercial/airline transport etc. Oz system uses a fundamental licence that gets its functionality 'expanded' with the addition of various ratings.
As aI understand it, a person with a Private Airplane Single Engine Land licence has to do a complete licence test for the issue of a Private Airplane Multi Engine Land.
I would have thought there'd be credits allowed though?