It might depend upon the climate where keissfamil lives. In a dry, arid climate a moisture-retentive mix is fantastic. But in an area with humid weather and high rainfall it could be deadly for the plants, for sure. I always cringe when I see people taking home "moisture control" potting soil in Florida. Just hope they're going to grow something that likes its feet wet.
It also depends a bit on the soil underneath the raised bed, doesn't it? If it's sandy or rocky, the bed will drain fine, but a clay base would be a problem.
