first of all kids are now allowed in any office.
In my opinion there is some logic through which they are picking up the application, which of-course we do not know. You are absolutely right that some of the July applicants received their PPR and some are still waiting for their MR... but I have a doubt
Why they are taking time between PER to MR ..
I think coz this the stage where the background check of your employer , degrees , certification will be follow,, now the scenario depends on the employer response in terms of telephonic or email discussions... Then checking of degree validity and originality is also not an easy task in India, so may be this process will delay applicant file processing also.. Suppose I have Degree of Delhi University and some one have Degree of Bihar University ,, so checking up Delhi university degree is easy and fast process compare to Bihar Degree.....
similarly after MR VO checked your Criminal background and security check,, same theorem applies here also as criminality check for different countries may take time compare to the person who is having one PCC only... or Criminality security check is easy for applicants residing in MUMBAI rather then Jhansi...
So this may be the point of delay....