I gave my reasons why I wouldn't..
I don't see the benifits of it at all..
What's so hard about explaining your reasons? All you did was give a vague judgement that "stuff" would somehow accumulate in the holes that nothing can get to. I've asked twice now for an explanation and have not gotten any response whatsoever. It doesn't help to just keep repeating vague, and IMO
If the egg-crate is on the bottom, detritus should not be reaching the lower levels of the sandbed to begin with. If it does, there are the obvious problems of accumulation that have nothing to do with the egg-crate itself and are an indication of a much larger problem. If the egg-crate material is off of the bottom, there are again no worries as infauna travel horizontally and vertically through the sandbed.
The obvious benefit in this case is the reassurance that nothing will happen to the tank from the rock. The likelihood of it occuring is not all that relevant, as no one can say with absolute certainty that something could or could not happen. The shrimp/goby combo is also actually a reason FOR having the barrier somewhere in the sandbed...as the last thing you want is livestock burrowing down in the bottom layers of a functioning sandbed
I'm not attempting to create an argument, but rather seek out answers based on supported information, not guesses. If factual information is available, it would benefit all to see it.