Contractor's Signature

What is the significance of FAR 4.102 Contractors Signature? By and large, it appears to be disregard.

In my experience, the Government strictly stands by expressed and actual authority for it's agents but, it appears government contractors aren't held to that standard and implied or apparent authority is good enough to bind them. This doesn't appear to track with FAR 4.102.

Are any offices actually following FAR 4.102 to a T?