Client change within 15 miles and h1b amendment


I have an approved petition for 2 years and my client changed. And the new client work location is within 15 miles of previous client(as per petition), Role is same.

Question: Should I go for an amendment ?
My employer says: any customer change irrespective of anything, we need to go for an amendment and its illegal to work without amendment.

what is the actual policy as per USCIS ?

Thanks Advance for your help