It's conterproductive to a sandbed. It feeds on the very things you try to produce. The post that you read that said that they were ok (IMO) meant that sometimes the sandbed production is far greater than the sand sifters detruction.
I have a sand sifting star with a dsb. I brought it not knowing that the two don't mix. It's ok because he's not that big and I have a 125 gallon tank. Hope this helps.