Curiosity
The Royal Mameluk are skilled shooter and when upgraded with arm/hrs and gaining shoot and charge they keep the skilled most other similar guards units in other lists lost.
is there a reason for it ? or did I miss something
A view seeing them as a bit more shooting heavy than some others who are a bit more fighty - so they are Skilled shooters and Superior rather than Experienced shooters and Exceptional as such as Mongol khan's guard or the Timurid guard are.
Its the sort of difference you can spend hours talking round in circles about as there is no obviously "right" grading, but produces differences between lists which is nice to have.