That is a beautiful quilt. I am a pre-washer but in this case I would not. The craftsy site even advises against it on the link you provided. Bernatex is a reputable manufacturer and they make beautiful quality fabric in my experience. I would bet these gradation fabrics are colorfast. Make the quilt then wash in cold water with color catchers and synthrapol or blue dawn dish detergent in a top loader washing machine where you can control how much water, use lots, wash as though this was an extra large load.