Just one of the thousands of things the (D)Umbshits don't comprehend, or simply choose not to, because narrative. A good example is Federal Civil Service Technicians. They don't pay into SS and don't receive any. ARNG GS/WG techs, anyways. This is all known at the start of employment. They still double dip by drawing a military retirement, on top of their civil service retirement.
I don't know where you're getting that from. The provision the DUmmies are talking about applies to public pensions that are SS-exempt. Military pay has been subject to SS since something like 1956, and all the Federal civil service pensions from the mid-80s onward use a system called FERS, under which they are subject to full SS withholding and the SS payments are integrated into the pension scheme to pay a greatly reduced CS retirement amount compared to the old system; it isn't 'Double dipping,' it's an integrated total payment with two components.
There are folks left who began under the old system, known as CSRS, which was SS exempt, when FERS came in they were allowed to either keep the grandfathered system or switch. Time marches on, and fewer and fewer of these grandfathered CSRS folks remain in the work force each year. A smaller and smaller number of these grandfathered CS workers remain in civil service, after FERS began, all new hires entered since then entered under FERS.