I use my Vessica as the clean bottle. I got a Vecto bag and filter as a kit, so I use that for dirty water. I scrunch the Vessica before squeezing the Vecto so there’s less burping needed.
I would think the rigid bottom and top would make squeezing dirty water out of the Vessica might be good ergonomically until the top and bottom meet. There would be a fair amount of water you couldn’t squeeze out. Also, I’d worry about putting too much pressure on the welds between materials.