supporting data on rinsing/what is removed comes from large scale fish production facilities and how/when they handle rinsing and backflushing of filters.
A massive amount of competing strains of aerobes, some anaerobes and their floc (detritus) are rinsed away in backflushing...what we do in the thread is like backflushing of the old beds, so that they can begin storing up waste again till the next manmade or ladymade storm. Bacterial aggregates that aren't associated with high flow environs build up in a biofilter...they're meant to be rinsed off as rivers surge or as oceans churn in a storm in nature, the life forms that are associated with high flow areas (biofilter zones) are adapted to stick in place with biofilms, nearly permanently locked into place regardless of the degree of physical rinsing/washing going on as long as there's no medication aspect killing them.
some reefers choose to rinse occasionally or pre siphon out waste like in Blusop's thread so they will not kill, or wipe out the whole tank during a move, a powerhead dislodge, a rock stack slide etc.
the pre rinsing of brand new beds is for silt removal, high fraction silicate Ive linked a discussion with Randy in there about how that feeds early diatom headaches. It in the least removes visual headaches...half the posts right now in the new keeper forum regarding bac blooms are actually sandbed silt issues.
rinsing eliminates early confusion, begins bio trust, allows me to eventually sell people on killing their early invaders vs storing them and allowing the tank to become invaded from the bottom to the clear top....imo all of this works in sequence to lend the uninvaded, reefer in control aquarium approach.
I can't think of one scientific benefit of not rinsing new live sand, not one. all of them stack on the rinsing side...
of course there's debate in reef circles about rinsing the living old sand, after all we're the only branch of the aquatics hobby that teaches that a biofilter both exports, mineralizes and resets itself in perfect balance, the rest of the world is having to rinse to keep up long term production.