It's usually best to wash dark colors separate because of the possiblity of bleeding. Just like clothes, separate the lights and the darks.

Which is why the black and white shirt is always in the "don't know which load to put it in" and ends up being a left-over that I eventually wash by itself.

I always end up putting the 'don't know which load' clothes in the darks. I figure I'd rather ruin one shirt than a whole load of whites. I think only one has gotten dingy on the white parts-it was a shirt that was like the layered look with a black tshirt over white sleeves. DD doesn't even care-she wears it anyway.

It depends on what your concern is ...is it shrinking or is it running.
If you like the puckered look and are not concerned about running ... nope no need to pre-wash.
If you are worried about running/bleeding , soak in a sink and rinse ( unless batik then pretreat with Retayne) , then you can dry on a hanger or rack.
If you do not want the Puckered look and want the quilt to be as flat as the day you ironed the blocks , yep you need to get the strips completely wet , blot dry on a towel , then use a dryer delicates bag to dry. I would not use the washing machine for get them wet , the agitation will cause raveling.
If you are concerned about finishes the manufacture puts on the fabrics ... hand wash/soak using 1 gal water with 1/4 cup white vinegar and luke warm water. Rinse twice and line dry.

I agree. Use the all or nothing rule.
Karen