It's possible to overthink this IMO. 'Injection' implies a bolus delivered directly into a person with a syringe, not something added to an infusion. That's how I would have interpreted this question anyway.
Which is what I said in my first post.That could be either in the giving set (unlikely due to sensors in the pump, and the likely presence of a filter) or direct injection near to the baby via a rubber port or a 3-way tap. What they just indicates the route not the method.