It depends on how you define easy. Mile High Club is considered one of the hardest achievements overall, however there are people that beat it in a couple tries (myself included
), they would call it easy. There are also games that require mindless grinding for hundreds of hours, but takes absolutely no skill at all, which can also be considered easy. This game falls in between I would say. The hardest difficulty does take some skill, yet it isn't a very long game. But there are some people that just cannot do it on hard, they wouldn't call it easy, just like the people that have sunk hundreds of controller shattering hours trying to pop Mile High Club, basically it is relative. A 7 is a good number on the guide, it lets people know they may be in for a challenge, but not brain exploding frustration for most seasoned gamers.