Bias vs On grain

[sewingrandma]

I have a pattern Mcall's 6563. It is a top with cowl neckline. The front is supposed to be cut on the bias and I know how bias clings and I don't need anything that clings around my middle right now. The discription states fitted pullover and calls for soft lightweight wovens or stable knits. Everyone on Pattern Review raves about it but the pictures are hard to look closely at and only one person cut it on grain and she didn't mention how it fit and her pics were really bad. Anyone have any thoughts other than make a muslin to see? Thanks.