I don't think they send out our info to the home country to separately check. My manager got his approval in 3 months. By the way, in 2005 (before retrogression started), the processing time was between 2 and 4 months. It is impossible to get the info within 2 or 3 months.
No to mention, I really doubt there is a "database" in India where everybody's record is kept.
I have looked through the standard operating procedure/protocol for 485 (link
www.ilw.com/seminars/august2002_citation2b.pdf ) which walks you through each step of processing of 485 including where they should place the documents and clamp/staple. There is no indication there they do background check in the home country. The instruction asks them to check the name against CIR (some index) and that is it and of course, they rely on FBI name check. If there is a hit, it is possible that FBI might seek records from the homecountry. I don't believe every applicant will get his record checked from home country.
Not to mention, there are many under developed countries, where it might be even more difficult to get background info.
It is interesting to go thro the steps involved. You will be surprised to see that there is barely 4 to 5 steps (such as ensuring fee is there, 140 approval is there, name check clear, etc) before approval. So, they might be touching files only for 4 to 5 days with lot of gap inbetween each step. Most time goes by waiting for the file to be picked up after each step.
Ela