I think many of the things mentioned above are very common everywhere. When having met other exJW's and they say what they did on field service it always bring the the reply "I did that as well"
When a Min Servant I used to help the Service Overseer and often would see report slips. I would see the report from some brothers/sisters and think how did they do that many hours, I only saw them out a couple of times. One MS assigned to a distant group, would speak to someone in his street, drive the 20 mins to the territory, do 20 mins door to door then go, drive 20 mins back home speak to someone in his street and count an hours service.
Often I would hear the Service Overseer when it was time for reports to go in. Say to usually elderly sisters, who had forgotten to put one in, to "Just stick a couple of hours down. So we don't take it your inactive."
I've watched JW's in my street work their way up the opposite side to mine. About 40-50 houses and make it last an hour. Stand on corner talking. Go to first house. Knock on door (gently) stand talking, leave door, stand at gate spending 2-3 minutes writing it down as a "not at home" go to next house, repeat. Get to end of road stand talking. Look at watch. "Hey we done our hour, lets go for a coffee." Walk off, looking a lot happier than they did before.
As someone said , just how accurate is the yearly report.