An admitted error like that (dealer not knowing his product manufacturer's warranty period from the get go) would make me wonder what other errors might have been made in the sales pitch. I would really go over the ext warranty with a skeptical fine tooth comb before agreeing to it. As cekkk and others have said, whoever is pushing it probably stands to make some bucks on the deal, so check it out thoroughly.
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Mindi (dachshund)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.