That's where I disagree. I don't think it's about confidence with Morata at all; it's simply about him being this kind of player.
During his professional career Morata has scored 82 goals in 232 games. That's a goal every 2,8 games, basically what he has been scoring in the past 13 PL games (4 goals) ever since his hattrick against Stoke. Do I think he will continue missing a sitter per game? No, I don't. However, I do expect Morata to continue scoring every 2,8 games. When he stops missing every 1-on-1 he'll probably top out at a 2,3 rate but generally speaking this is just the type of player he is. He'll always be frustrating because he'll always leave you wanting for more. He's been this player at Real and he's been this player at Juve: very good technically, strong in the air, consistent in his overall contribution but simply not a killer in front of the goal.
IMO after over 200 professional games you kind of are what you are. Players rarely change dramatically after that number of games and Morata suddenly becoming clinical would a dramatic change.