Coaches, most coaches, might change their mind and make line ups out differently.
Most coaches can watch a round or two of batting practice and figure out who their best hitters are. A round or two of infield and figure out who their best infielders are. Watch them throw and figure out who has the best arm.
Usually the top several standout and are easy starters. Usually there are a couple spots that require making a tougher decision. Left handed throwers don't have a future at positions other than 1B, OF, or LHP, so playing any other position is kind of out of the picture.
Sometimes we see coaches play kids out of their best position. Sometimes it just happens because of need. However we have seen a few of the very best pitchers in their state, that were not used as pitchers on their high school teams.
Anyway, it's really not very difficult to watch 20 kids play baseball for a couple days and figure out who has the most talent. Though I must admit, there has been some very strange things happen. One of the most talented kids in the country in the 2016 class did not start for his high school team. In fact, he hardly played. He would have been his HS teams best pitcher (93 with a very good breaking ball and great command as a sophomore) and he is an even better position player and hitter with power. He will be a good draft pick in 2016. He also is a good kid and team player who plays hard and loves to compete. He actually was one of the stars of a highest level national summer team. Not sure if anyone would have known about him had he not played for that team.
So mistakes do happen, for one reason or another, but if a player has what it takes he can overcome those problems. Talent sticks out like a sore thumb and there are many people that can recognize it.