I think in the UK, there is too much training where logic and common sense should prevail.
All forklifts work on the same principle, work in different enviroments and locations but still do the same operation.
I think unit and site familiarisation is more important than having to get a separate licence when a person already knows how to drive and operate a truck in a responsible manner.
I have seen where youngsters and older persons alike have done a course and obtained licences for forklift trucks yet have not actually worked in a production enviroment.
This has led to some accidents when they have started work as they were not taught how to drive the units in an actual production enviroment.
I have an operators licence for all trucks as I used to work on them but the test and course to obtain the licence was all done on a flat surface and in a controlled enviroment.

My personal verdict is, one licence should be sufficient as long as the individual has the sense and responsibility to operate one in the first place