starch often will help (stiffen) pre-washed fabrics so they are easier to cut precisely- if the fabric has not been pre=washed a spritz of water usually does the trick-since the sizing has not been washed out.
i've been using plain ole Niagra spray starch for 47 years---my mom & grandmother both used it-
i starch fabrics when they need a little more than what water can do- or if i want the fabric to be stiff for some reason- also it really helps when cutting flannels for good cuts. i do not use it to try to (force) blocks- seems like when the quilt was washed the blocks would be back to being (wonky/wrong)
i do not use the 'best-press' or other (designer) starches/sprays---i don't like the smell of them- i pre-wash to get rid of any stink in my fabrics- i don't want to then add a new stink - with plain old niagra there is no lingering odor on my fabric.