One of the reasons I wash all washable components before cutting them is because I have had experiences like yours.
I decided that I would rather spend the time "up front" with the washing and drying - and not have to again deal with uneven shrinkage and/or bleeds.
And when it gets wet again, the fibers will revert to the size they want to be.
There are some that believe that dense quilting will stabilize/minimize the shrinking/reshrinking. I do not know if these inidividuals have measured the size of their items before and after washing them or not.