Actually from the link you will not find the JD. JD is like when any employee join the company, company should provide the detail job responsibilities for that employee. It is almost same JD for same job title from same company. But ref/Job role letter could be the main major points of JD, could be 5~6 points not more than.
For example - A company has two Merchandisers and their JD is same as the same job title. But their main responsibilities could be diff like one Merchandiser can work on Woven items and other can work on Knit items. There is huge difference on both items/role from company perspective.
Hope it will give you some idea. ...
Bhaiya i got it from the link u gave and being a HR employee, i understood what it meant, it is the same u said. In JD we provide a lot of things in detail, but in any reference letter, we just put the main duties.