Of course it is, that is the nature of larger particles vs. smaller. The crushed coral will always trap excess food and detritus, and will ALWAYS need to be vacuumed before this waste deteriorates and coverts into nitrates. Now if the sand bed underneath does what a sand bed should then its going to get some anoxic regions or areas of no oxygen, this form of bacteria if released into the water column while trying to vaccum that crushed coral and wipe out a tank.
Make no mistake you will have to vaccum that CC and you will desturb that sand bed, and the CC will trap waste and cause water problems, least that has always been my experience. There are some folks that have never had problems with crushed coral, but they are few and far between.
Thomas