Sure, injuries happen and some people have great camps, but I would venture that the final spring depth chart is 80% what you will see in the fall.
Also, Loyal Cougars isn't really the legit depth chart. It's just a guess and usually taken from a combination of the real one and what they hear from practice, etc.
Additionally, Loyal Cougars depth chart is a thing of art. They spend hours every week scouring practice reports and even talking to coaches and players (and occasionally just fans and media) about who took what reps. You're never going to get the legit depth chart but again, LC does a great job getting us closer than anyone else.