You know-- it might be the model's canted hip pose, also, that says that. So on a real person...could be different. I hear what you are saying about the woman you know who wears tight dresses that do not look overtly "sexy." Some has to do with a person's body language, too.

The zipper strikes me as very slightly edgy, not sexy, and I would find it very appropriate for business attire, especially with a topper or jacket over the top. IMO, if someone thinks of "unzip me" when they see it, that's their issue and not mine. Then again, I enjoy hardwear and high contrast metallics on clothing, so there's that. As far as it being body-con, I think that all depends on one's figure and the size one orders. I typically do not wear things snug, so if it were tight or too curve-hugging, I'd either try a different size or not choose the dress. Often a size up will allow a dress to skim the body without looking body-con or snug and without looking too big.

I think of the zipper as adding a "tough" element, rather than a "sexy" element. I have a few pencil skirts of the type UF describes that have a zip at the side, front or back. I think the zip adds an interesting twist to the traditional pencil skirt.
Of course even a "tough" design detail could look out of place in some more conservative work environments, so I agree with others that it still depends on the circumstances, and with what you are comfortable with.

What a great dress! I find the zipper adds a nice point of difference and do not see it as being inherently sexy.

I wear sheath dresses to work often, however I stay away from them being very fitted which is my personal preference. How you wear a dress (topper, posture, hair, make-up etc) all have a part to play in how professional this dress will look too. If worn with a blazer or jacket, it will de-bombshell the dress. I would keep my hair and make-up soft and natural looking. I work in a rather conservative professional services firm and would happily wear this dress, but I may take one size up just to keep the fit a bit more fluid and less fitted.

Zipper? Not a problem any more, as several have noted. Shape? That may be an issue, but layering a nice blazer will make for a professional appearance. From there, it depends on the workplace or church culture.