That is true. But there is really no "military" reason why Ewell delayed his attack on the Confederate left by 2 hours after Longstreet began his assualt. Wright's Georgia Brigade broke the Union lines on cemetary Ridge and achieved the success that Lee was looking for but Hill failed to send forward the next brigade in the attack and left Wright's Brigade unsupported at that critical moment.
It is my belief that IF Longstreet had had Jenkin's brigade, that had been left behind to guard Richmond instead of relying on Beauregards forces to protect Richmond, He (longstreet) and Hood would have effectively had their force to flank the Union position at Little Round Top as they wanted to do. Whether Jenkins would have been used to extend the line, or deployed as support, it would have been the same difference. But since both Hood's and Kershaw's Divisions had been deployed in two lines as their own support, I see Jenkin's being deployed in line in the same manner, thus extending the line.
It is quite clear from most of the Confederate accounts of men in the field that Little Round Top was occupied before the Confederate assualt started. That Law was directed intentionally to Little Round Top. Had Jenkin's 5 regiments been deployed where they swept behind the 20th Maine and Little Round Top they would have gained the Union rear and Sickle would not have recieved the reenforcements that he did that made the Wheatfield and Peach Orchard as bloody as those Battlefield were.