I would definitely want to know.
I used to handquilt for an older lady with a small shop/business. Once she sent me a top that had all the same kind of blocks. It was a commission quilt and she said her daughter had pieced it for her. As I was quilting it, over 50% quilted, I noticed one block near the edge was significantly smaller than the others, causing distortion in the blocks around it. I felt awful that I had not seen it before (she did the basting) and went back and forth about whether to tell her about it. I felt bad that it was her daughters work, did not want to bad-mouth her daughter, but then I thought about the customer, knowing I would feel bad if I got that quality of work in a quilt I had paid for.
I did tell her, and she said to just quilt over it. Not sure what happened when she got it back.