Please expand. Does a LG need longer arms than a RG, if so why? Same with lateral movement? Not trying to be a jack wagon, just trying to understand why a guard is any different depending on which side of the center he lines C up on.
*not a football expert by any means, but my 2 cents*
the right side has typically been the "run" side, and the left side is typically the "pass" side. I think its a formational thing just based on the quarterback usually being right handed.
Two things from that, first is the blind side is going to be the opposite of the qb's dominate hand, the left for most guys, so you want guys who can pass block better on the blindside. not just at the tackle position. especially when you consider defensive fronts that use wide splits on the blindside DE, like we do with Pearce. That pulls the LT way off to one side when he goes back to pass block, so the LG is left in more space than his counterpart on the right side. so better feet and longer arms are more impactful on the left side in pass block even for the g.
the second item comes down to how running plays typically develop. usually the RB starts on one side and then goes across the QB to the other side on their route. Not all routes do that, and obviously if they have good eyes and feet the RB may do something different. to make sure the RB gets the ball cleanly you typically want the ball to hit the RB first, not the back of your hand which can cause fumbles. that "mesh" between RB and QB handoff is extremely important in a RPO type play call where the QB is reading the defense as the play develops so there is a little more risk and timing there, so having your dominate hand on the ball is better than your off hand. a lot of formations start with the RB on the left side of the QB as that will have his dominate right hand on the ball longer, and it allows the RB to help in pass blocking without giving up play call. on the left they can block or run, if they are on the right side they have to stand in a different depth which typically is a key the defense can read. it also allows the QB to hand off and throw with the same hand, instead of tipping off the defense if the QB was using left for running and right for throwing. so in the case of a right handed QB most running plays by the RB are designed to go to the right. obviously some huge schematic preferences come into play with that last statement.
it also just lets you play to different guy's strength and benefit the most from them. not every Tackle or Guard, is going to be as good at both skills. so its better to group similar skills, and if the left side is the pass blocking side, that naturally leaves the right side to be more of the run blocking.