I am an advocate for prewashing all washable fabrics before cutting.
I strongly suggest it for ALL fabrics that will probably need to be washed at some point.
It's part of that dreaded "prep work"
Imagine my "shock and dismay" when I was looking at some instruction sheets at WalMart - displayed above the precut fabrics - that started out with "do not prewash your fabrics . . . ." then the instructions go on to list the precut fabrics needed to complete the projects.
What the >>>> ????
Also, in many cases, there is more than one "right way" to do something - if the maker is pleased with the results - or has learned a few things in the process - it's been a successful project. It doesn't even need to get finished, to have been useful. (Think of math homework in school - how many of us have those papers yet?)
It's okay to change one's mind about a process or choice -
One can make an elegant quilt without a fancy sewing machine. Many of the old ones were hand-pieced (wonder why we say "hand-pieced"? Wouldn't "hand guided needle and thread pieced" be more accurate?)
It is important to have any machine working properly, though.