imo, 60" wide is good for baby quilts or twins only and 4 oz per yard is thin. whether or not you like like poly is a personal preference. in the washing, you won't get the wrinkly look that you get with cotton or cotton blend battings.
if you wanted to make adult bed quilts, you would have to stitch 2 lengths together, so there would be waste and what would you do with that? you shouldn't use it for anything hot because it can melt.
btw - why is she saying she wants to sell?