Then you both misinterpreted the point of FTP. FTP does not and has nothing to do with hour power. UNLESS, you are training for a TT. FTP is a training tool to set training zones. Which as @stevemz stated would be your ability to hold your FTP from 30-70 mins.
Why would I ever want or care about some theoretical “hour power”, I race XCO so my actual hour power is useless knowledge and certainly something I would never waste my valuable training time on. FTP is a proxy for one’s maximal lactate steady state (MLSS) and work load (MLSSw). Your FTP allows one to train at appropriate power levels. Then, through training you chose how to express your FTP depending on your cycling discipline and goals.
For example, two riders at 5.0 w/kg with the same age, weight and height; but one races road centuries and the other races XCO (or crits), may have the same (and accurate) FTP, but are able to express that FTP in vastly different ways. It does not mean the the rider with the sustained ability to hold his FTP for 70 mins is somehow better. I assure you that specialty trained century rider will not fair well in a crit.
This “hour power” thing is foolishly traditional thinking and an ignorant way people use to minimize/belittle another’s stated FTP or w/kg.