that may be so, but did you ever stop to think that perhaps, and I say perhaps, his paperwork wasn't correct. From my experience those that use an agent fall into 2 categories: #1. Taking a shortcut because they don't meet the requirements OR #2. They're just too lazy/incompetent to do it themselves and do it correctly.
I do my own extensions each year and have no problems whatsoever. Have the correct documentation and you shouldn't have any issues, unless the IO is having a bad day, and that's usually because they keep having to deal with foreigners that don't have their documentation correct and who want to stand there and argue with them. I've witnessed that on many occasions.