Special Source Transformations
You are correct &mdash; if there's an extra resistor in parallel with a voltage source, the source will have to deliver more current. If there's an extra resistor in series with a current source, the source will have to deliver more voltage. In both cases, the source must supply more power than it would without the extra resistor.

But the point that the book is making is that none of this has any effect whatsoever on the analysis of the rest of the circuit. From its point of view, the source looks exactly the same with or without the resistor.