Firstly watch this.
This is CONFIRMED news. Moreover i feel 70 is just a minimum of medals you need to collect for the trophy. Or there are 70 KEY missions worthy of medals. Since the achievement clearly mentions "And strangers and freaks." That being said, i'm more than satisfied with 100 hours of single player. I don't see ANY reason to be disappointed. Even though i love CVG, i have more faith in Rockstar. Out here, let me know what you think will be in the game.