It was essentially a sidelight to the battle; having no measurable affect one way or the other. And it wasn’t coordinated within Longstreet’s attack. It was a separate engagement although it was meant to distract Union forces during the attack on Cemetery Ridge.
It’s mentioned both by Foote and McPherson in their volumes on the war.
My point was that the author I read thought it was much more than a side light and that it was coordinated. In particular the author noted how Stuart fired a cannon before Pickett's charge to indicate he was in position and that after action reports made reference to Stuart's part of the attack as sweeping down a road to attack the Union forces (who were being attacked by Pickett)from the rear. However, it failed because Custer intervened.