Yeah - folks talk about height and sometimes quibble about a lock's height difference of 3-4 centimetres with great seriousness, when it can be a bunk comparison.
If a taller player has a long neck and a shorter one a shorter neck, their shoulders (read arm sockets) could start at the same level - yet we crow about the taller guy.
Then if the taller one with the long neck also has short arms, and the the shorter guy, long arms, you could find that shorty can actually reach up higher.
Further, if short neck has a good vertical jump he could be more easily lifted than long neck who is a pot plant, because the lifting effort starts higher off the ground. Then you have to take into account the skill of catching the ball and especially catching it at full stretch even over the opponent's side of the line of touch. And then you have to think if the bloke can have soft hands, or one soft hand, with arms at full stretch, like an elite slips fielder going for a wide, high catch.
I imagine that the guys with the clipboards at super outfits get potential lineout jumpers to raise their arms and measure how high they can reach up standing still. They would also measure their vertical jump as NFL guys do for their wide receivers and corner backs and safeties. Then they would measure the other stuff which is done with their eye and not with a tape.
Yeah - sometimes 3-4 cms in a 2nd rower's height can be neither here nor there.