I think a little bit of chest slack in a 'hard'-shell jacket is natural in certain positions - namely in the drops.

If the jacket was completely tight over your chest while in the drops, you wouldn't be able to extend your arms fully out to the sides while upright.

I have a Showers Pass Elite 2.0 jacket, and while it fits perfectly, there is a little slack in the chest area while down in the drops. If I have too much stuff in the chest pocket, it will bounce off my thigh when I'm really low and hammering. Other than that, I never notice it and don't consider it an issue.

On the other hand, my Castelli partial jacket is a soft shell and is generally quite tight on the chest. Euro sizing is perfect for us 135lbs types!