The listing agent probably told you what the seller told them. Our MLS listings contain language that says:
"the accuracy of all information, regardless of source, including but not limited to square footage and lot sizes, is deemed reliable but not guaranteed and should be personally verified through personal inspection by and/or with the appropriate professionals."
in other words: Caveat Emptor (buyer beware)... it's the buyer's responsibility to confirm everything that's important to them.
It's very likely that it wasn't an attempt to trick you... It's very common for a seller to tell me that the furnace is only 6 years old, and when I have them produce the invoice, it shows that it was installed 10 years ago... it was an honest mistake... it just felt like it wasn't that long ago.