I'm certain there was no reduction in standards for William and Harry when they went through military selection and training. However, there was one particular thing where they did indeed receive 'special' treatment.
Prior to them attending the DHFS helicopter course, the course did not comply with CAA/JAA requirements for PPL(h). Quite a lot of work was done to ensure the course became compliant so that William and Harry could get their PPL(h) without any further training. Things like a qualifying solo cross country navex, vortex ring recovery training in the simulator, revisions to the ground briefings to include LTE and an air law exam were included. This work would not have been done, had PPL(h)s not been a secondary target for the Royal brothers.
Prior to their attendance, the UK military had pretty much actively discouraged their pilots from getting licenses and certainly had not moved the course goalposts to fit. Indeed, several years after they left, with the onset of EASA regulations, guess what? The course is no longer compliant and the military have no interest in making licenses a priority for our serving lads and lasses (at least that was the case 12 months ago, and I've no reason to suspect that it's changed).
Don't get me wrong, I'm not having a pop at the Royals here. I just dislike the sycophantic way individuals within the military hierarchy moved heaven and earth to accommodate the Royals, when they wouldn't move an inch to accommodate, or reward, the career aviator/soldier.