Your still not understanding, he was saying it is impossible to really know the age without background info. In most cases when you buy a large fish it is stunted. Just because most people on here take good care of there fish doesn't mean the rest of the world does. I guarantee at most 1% of the worlds fish keeping population is on this site and the people on this site are hardcore enthusiasts; even with that knowledge there are a lot of people on here that don't provide the proper conditions for fish. So you got to do the math, the majority of fish keepers in the world are just ignorant to the proper mechanics of fish keeping.
That being said people with your knowledge of fishkeeping should be out educating people. Just remember no one wants to learn from some one who is condescending and insulting. I hope you you will spread your knowledge to many people because the world could benefit from what you have to offer.