It has long been the case that they recruit from among the Specials, its always been a 'back door' entry method, and now they are doing the same with PCSO's (although to be honest their starting pay is almost the same now, but they have less responsibility and can legally walk away from trouble, so why become a copper?), however;
1. It gives the cops a chance to have a good long look at you, instead of the 'snap shot' glimpse that they get when you turn up for recruitment.
and;
2. It gives future recruits a chance to pick up some knowledge of police culture and learn the jargon that helps in the recruiting process, terms like 'Community Policing', 'Policing by consent', 'Issues of diversity', 'Positive discrimination', 'I am gay/black/muslim/ Asian/ 4' 10" tall' or 'I will have no hesitation in putting in a 'Grievance' against any colleague who upsets me, especially if it means I can get promoted or a cushy job, or else I will report sick with stress until I am returned unfit and pensioned off or I will sue the police for damages' etc etc, and all the other jargon they will need to progress in their career. (sorry, perhaps a bit of cynicism creeping in there)