The article, which is thin on detail, implies that the support requirements are probably for specialized equipment (not owned by, or trained, by the Services) or for functions that require specific expertise. It is probably more cost effective to do it this way, particularly in deployed areas. It doesn't require a force plus up justification, and can easily be expanded or contracted numbers-wise to meet needs.

One thing about which it is important to be clear: this contract supports US Special Operations Forces. This means all of the various SOF entities provided through all of the Services.

US Army "Special Forces", one small part of the larger SOF whole, has pretty robust organic logisitics capability, and receive the appropriate plus ups when they execute a SOTF/JSOTF mission. However, besides Army Special Forces, most SOF entities by design have pretty thin organic, uniformed logistics support.