As an ex 46th St Athan B/E I can neither confirm nor deny an `official` policy existed.
...However - During ITS we were told by various people (senior entries, DIs, Station Barber) that we were lucky because the last of the `Borstal Entries` had graduated before we got there in May 62. They had, apparently, ruled the camp with an iron fist. We had several of our number (no names, no pack drill) who had been given a stark choice of Gaol or becoming a B/E by magistrates....Nonetheless, Senior Entry `perks` still remained right to the very end, I gather. Must have been hard for the 51st as they had no one to lord it over....
IIRC the hardening up process (AKA bullying?), was encouraged by all - including staff. I personally will never forget the misery inflicted on us by a certain sadistic PTI during entry swimming periods - nasty piece of work IMHO. On balance, however, I think it (B/E training) did me and most of my compatriots good. The Tech training was excellent and set us up for our future careers.