I think most of us are talking about washing the quilt after it's done - meaning after it's been quilted and the binding put on.
Just washing the top is to be avoided if possible - because of threads raveling, seams coming apart at the edges - occasionally it has to be done - one of my cats anointed something I was working on - I noticed it when I was pressing it - wretched creature - thought I had it out of his reach -
I soaked it in the tub, let it drain as much as possible, and draped it on a drying rack. Then had to press it again. The piece edges are frayed looking now - I had to resew a few of the edge pieces.