As an aside I think Longstreet gets a "bum rap" he seems to have been right: Lee should have early on gone around the left flank of the Union army.(Lee's right flank.)
Even the oft maligned ‘Pickett's Charge’ was a viable plan, one that went awry due to the poor aim of the artillery bombardment which failed to accomplish it's task.
Studies such as this one are usually informative to those whom are relatively uninformed. On the other hand, it does provide updated teaching opportunities to the students, which is probably what the whole point of the study was about (as opposed to adding any real new insight).
Longstreet was right one hell of a lot more than he was wrong. Unfortunately, he always seemed less than enthusiastic in carrying out orders he did not agree with.
IMNVHO, Best general in the Civil War on either side: General George B. Thomas, victim of a PR cabal by Grant, Sherman, Schofield, and their pals in DC, all of whom admitted it long after the war.
He was an all-around guy, a master of logistics, engineering, training, cavalry, artillery, and maneuver on defense and attack. Careful and methodical, he took very good care of his troops and tried to minimize casualties.
Genius, especially when compared to Grant.
People do these studies because they need to "publish or perish". Better this one than "Homosexual Themes in the Writings of Geoffrey Chaucer".
On the first day of the battle, leading elements of both armies met at Gettysburg, clashed, the North moved to the the high ground and the South failed to dislodge them.
At the beginning of the second day, Longstreet advised Lee to disengage and move towards Washington in order to look for better ground. Lee decided to stay, fight and took heavy losses for the next two days, losing the battle.
On the other hand Lee did give Stuart his orders and if they came back and bit him then you can't blame Stuart for that.