I think you misunderstood. When you are by yourself, go for the harder shots. It's a form of practice. If you practice the hard shots, the easy shots, get easier.
I just played in a 2 man scramble tourney with a guy and we shot a 63, he laid up....and I went for it. I never would have hit any great shots if I wouldn't have ever practiced hard shots.
What happens if you shank a lay up shot? You are forced to make something happen to save par.
Skip to 1:33 for the part I am referencing here:
In theory, practicing the harder shots in golf is not necessarily going to make the less difficult shots in golf easier. This methodology would simply result in the harder shots becoming less difficult for you to pull them off. For example, does an NBA player working on 3-pointers contribute to making his free throws easier?
I personally practice more risky shots as well when I play solo or a round where score means nothing and doesn't go towards my HC, but I definitely do not do so with the idea that it is making less difficult shots even less difficult.
EDIT: I know that nobody here is on level with Phil, but the point goes to show that sometimes the creativity that more difficult shots inspire within our own minds, the more we are able to visualize a shot and produce a favorable result. Sometimes, players forget or take for granted the practice from favorable positions to begin with - such as from the center of the fairway within 80 yards. This lack of practice will obviously result in a weaker point in your game.