People exaggerate the size of everything... like reptiles. Did you know there are place by me where 5 foot garter snakes appear to be the norm? I have a pretty good sized bearded dragon (she is about 18 inches) and truthfully she is one of the largest ones I have ever seen. I know larger ones exist but they are not usually your standard pet dragons. I had several people tell me that their pet dragons were at least twice as big as mine. A 36" bearded dragon. That's one big dragon.
I also noticed that when people hold their hands (or fingers) apart to indicate size they rarely get the corresponding number right. I've seen people hold their hands a good foot apart and say something like (she has to be at least 7 or 8 inches) or even the other way "he is about a foot and a half long" and they have their hands a foot apart.
Usually when people start talking about size I just tune that part out. I know foot long praying mantises don't exist in Wisconsin (or Northern Illinois) and I know ball pythons don't get to be 10 feet long.
Interestingly, as a fish store owner, I can tell you that when people are looking to get rid of fish that have outgrown their tanks the tendency to minimize the size is a much more common occurrence. I've had more than my share of "5 or 6 inch" oscars and tinfoil barbs turn into 10-12" tank busters sometime between the time they told me about them and the time the got to my store.