Thats right, none of these claims have ever been proven. Regular partial water changes are the only way to replace trace elements and reduce nitrate concentratrion via dilution. Unless 100 percent of the water is changed, nitrate will steadily accumulate. Its concentration forming a sawtooth pattern trending upward if plotted on a graph. This has been documented in numerous reputable publications.
Reducing Nitrate is only one small reason to do water changes, there are many chemical reactions that take place in aquarium water over time and trace elements present in seawater that become depleted. Marine fish continuously drink water and are more susceptible to poor water quality.
I dont know many that enjoy changing water, it's a labor of the hobby. Without going into the details, I believe its just a matter of time before a major die off occurs.