I also wash mine in the sink & spin in my salad spinner.

I overcast my edges of fabric I wash in the washer. Do you have an overcast stitch on your machine that resembles a sergre like stitch. i use this to sew my non selvage edges to reduce fraying. I don't wash very often, usually only things I embroider. Haven't washed for a quilt yet

I do prewash fat quarters. They are the only precuts that I do wash. I use the gentle cycle on my washer and I don't have much problem with fraying. I only use warm water when I wash and no detergent. Someone told me not to use detergent for prewashing, but I can't remember why.

Seems to me that if one has a concern for a large piece of fabric (bleeding, shrinkage, chemicals), that a small piece of the same fabric would have the same issues.

I belong to the " do not pre wash " group, but if I have any doubts I hand wash in hot water, rinse in cold water and drip dry my fabric

Due to allergy problems, all fabrics are washed as soon as they come into the house. I wash fat quarter in warm with detergent. I have a front load washer and don't find the fraying issue all that bad. There is some fraying which I just snip off as I'm pressing. Usually, the frayed edges will be removed when the FQ is straightened up before cutting strips, squares etc.