If the presence or absence of people can affect the size, wouldn't the fact that swimmers start out of water and dive in screw this up? Unless the boards were

If the presence or absence of people can affect the size, wouldn't the fact that swimmers start out of water and dive in screw this up? Unless the boards were mechanized/able to adjust after the fact to maintain the correct distance despite changes to the pool environment. I was imagining setting up the boards prior to the race, but if they are responsive that's different.