Is it true that t he main difference between sensory preconditioning and higher-order conditioning is that with higher-order conditioning, the CS1

Is it true that the main difference between sensory preconditioning and higher-order conditioning is that with higher-order conditioning, the CS1 and US are initially paired before the CS1-CS2 pairing; whereas with sensory preconditioning, the CS1 and CS2 are paired in the initial phase before the US is introduced?