Most quilters cottons can be classified as broadcloth. That being said not all broadcloth is equal.
As for the blend ... I think it would depend on a number of things ... how high of a poly content? Does that fabric pill? Will it behave( actually crease and not melt) in the pressing process if matched with 100 percent cotton. Will it look notably thinner or thicker next to the other fabrics in the quilt? Back in the day , when I first started quilting ( pre - invention of the rotary cutter) , 100 percent cottons were not easy to find , and many many a quilt was made with blends. "back in the day" we liked them because they did not shrink, did not wrinkle like 100 percent cotton. Even sheets had poly in them as to reduce the wrinkling. If it preforms well in the wash ... but the merging/ironing in the piecing process is a problem... consider using it for a backing.