The RF SIDs on 07 are part of CAD's noise mitigation strategy following a concerted campaign by the bunch of people who bought flats right under a bridge leading to one of the Regions busiest airports after it was built and then wondered why planes were flying over the top all day and night.
While the turn point is the same as on the normal DF coded SIDs, The RF track contains the turn much more accurately, so reduces the splay of ground tracks after PORPA. That coupled with the way an FMS handles RF compared to Fly-over then Direct-to slightly differently, means the aircraft is already banked into commence the turn AT PORPA rather than passing then rolling and therefore actually turns well inside the complainers.
Initially the use was voluntary but as the population of RF-capable aircraft increased the policy became that RF -capable should fly them unless otherwise advised.
There is agreement now that certain operators/types will automatically be issued the RF SIDs. If you don't want it, or you are not one of those agreed operators but you want to fly it, then request through PDC as stated above.