The R suffix called out RoHS Compliant.
Assmann has confirmed that the part number without the “R” replaced the part number with the “R” due to the part number unification. This change happened in 2014 and a PCN for this change is shown below. Assmann removed the “-R” from the old part number.
PCN-US-20140910-Cable.pdf (289.0 KB)
Sometimes, you may find part number with “-R” suffix in the other names from DigiKey product page. They are still a functional equivalent.