I had never heard of it either but I asked at my LQS when I they were given to me.
Actually, an old quilt was given to me that was really poorly constructed, not to mention being less than aesthetically pleasing. So I took it apart to salvage the blocks and make a new quilt. Fabrics/design/layout/setting. etc. are all set....except the time to do it. ;-)
I found BIZ in the supermarket - it's a powder but stocked with the special detergents like Oxy etc. It's very inexpensive.
I had NO problems cleaning the blocks first before sewing the quilt together.
The blocks are perfectly stable and nothing happened to the embroidery.
There was no agitation in the plastic tub.
And, quite frankly, I'd want to know if they were going to disintegrate or something before I put all that time and money into making the quilt.