Back when I was learning to sew, Mom tought me to always be suspious of Red , and Purple fabrics for bleading. Since my sewing constisted of garment making preshrinking was manitory. Remember all that gauzy type fabric of the late 60's early 70's looked great on the bolt but shrunk and wrinkled like no other. Learned my lesson the hard way after making a shirt out of that fabric as I did not want the pain of getting all the wrinkles out prior to construction from prewashing. Well after all me work .. only was able to wear it once ... it shrunk about 20 %.
Then came the world of Poly and the need to preshrink was now a thing of the past. .. as was ironing! 100 percent cotton was scorned by fabric stores and it was dirt cheap to buy as no one wanted the fabric that had to be ironed and was going to shrink.
Then the rotary cutter was invented and revived the art of quilting , and cotton fabrics became more prevelant and gained popularity. The lessons I learned way back had to be relived if to avoid some of the issues I had associated with garment making. Even though the industry has come far in methods of manufactring and printing... they still have not "solved" the fundimental issues associated with 100 percent cotton fabrics. They do shrink ( it just depends on how much) and no manufacture guarentees against bleeding/running. So understanding the potential issues , I prewash all most all of my fabrics .
As for the use of Syntropol or Retayne... when working with batiks specifcally , one wash is often not sufficent to remove the unset dye. This is where my "cheapness" shows.... I would rather spend the small amount of $$ to resolve the issue ONCE and for all than to find out later that the unset dye was not sufficently dealt with the first ime around. Some batiks specifically the watercolor will bleed almost forever till the fabric is faded beyond the appeal it once had. To preserve the original appeal of color depth .. yes I will pretreat rather than toss it ,or wash and wash and wash.
I have learned that each quilter develops a guideline they use for fabrics and what their comfort level is. This can be altered typically by an experience.
Sorry I got so carried away in my response.