Seems pretty reasonable to me.

If it’s a rough wireframe it can be just that, rough.

If it’s a pixel perfect mockup then it’s a contract for final product IMO.

Of course whether there are that many sets of eyes on it depends how big a co you’re working for!

Pixel perfect? So if a css box-shadow is 11px instead of 12px someone will notice? ...I don't think so

Maybe if the pixel perfect design is diff'd against the final product...