I have to agree with 67th here, at least in broad picture.
We can debate the relative merits of the Weikert's Hill line versus the Peach Orchard line as much as we want. The fact is that with elements of 3 corps the Union held the former line, but with 1 corps could not hold the latter line.
It's a question of numbers. In OTL Sickles has a salient, true. He also has 6 brigades in a single long line. The 3 divisions coming at him have 13 brigades, so not only gain his flank, but also can support localized breakthroughs.
If Sickles uses the same force to hold a line from Cemetary Ridge south to Little Round Top, in all honesty he's still in one long line. But now the Confederate advance is still fresh when it meets his line. Hood is still not going to be stupid, and disregard orders to send elements of a brigade around the flank. So we have the Little Round Top fight earlier than OTL, but simultaneous with an attack farther north. Sickles is still overwhelmed and falls back.
More importantly, the heavy reinforcements that Meade sends him - Syke's corps, and a division from Hancock, will get to the battlefield a maximum of 15 minutes earlier than OTL due to distance, and that's not enough. In OTL they went floundering through the Wheatfield and arrived long after Sickle's line broke. The best they can try to do here is to re-take the (relatively) high ground, but by that time you also have Anderson striking farther north.
What Sickles did in OTL is to buy time, for the Union to compress enough troops in the line of Weikert's Hill to make it a strong line just through force of numbers. Here that doesn't happen.