It may be the rule in theory, but they don't always enforce it. And it's even more of a farce when you don't have any bags to check.

Just the other week, I flew BOM-AMD and there was no stamp on the home-printed BP. There was no ID check either, except by the CISF pandu manning the terminal entrance. And that doesn't count.

Flying Cathay last year, we had no luggage and used the new common kiosks. No one asked to see a thing, until we were seated on board and someone came running to validate the passport / ID etc.