Had Sickles remained in position, most of those 14,000 Confederates would have been marching across his front, would they not? Their planned axis of advance was up Emmitsburg Road, in line perpendicular to it. Indeed, McLaws' division was to be on the left or west side of the road, fine for cooperating with Hood in the planned advance, but rather awkwardly placed if the two divisions had to swing right while under fire from Cemetary Ridge.
most of those 14,000 Confederates, or maybe all.....would the right of Hood's division, presumably still Laws' brigade, have troubled to march up and down both Round Tops, or just advanced up the valley of Plum Run? Plum Run would put them well behind the expected Yankee position on Emmitsburg Road; their intention was to hit Cemetary Ridge further north.
Even if Hood's line did extend as far right as the Round Tops, that doesn't automatically mean the Confederates take the Yankees in flank. Sickles' original position extended to the base of Little Round Top, and as we know he was conscious of the danger of letting the enemy occupy high ground overlooking his positions. He could either occupy it himself or call for reinforcements from V Corps or elsewhere.
The Confederates misunderstood the Union positions on July 2, and their main blow was poised to strike into thin air - until Sickles moved his corps up to where the rebs were expecting to find it. He did reduce his vulnerability somewhat by refusing his left flank, but that also created a salient and spread his troops over more ground than they could effectively cover.