So not necessarily, but very likely that's where it would be used.
If I'm serving a detention sentence on the weekend, and I may or may not have other duties in the reserve, I'm a private. What's the problem if I'm a sergeant when I'm in the armoury? Why am I not entitled to be a sergeant? I'm not serving my detention. Is the purpose of the reduction of rank while you're in detention to keep you below the rank of someone who might be looking after you, somebody who might be guarding you, or is the purpose punishment and loss of pay? If that is the case, then your detention and the loss of pay that runs with that....
If you're sentenced to 14 days not intermittently, say, you'll lose 14 days of pay between your current rank and that of private, and that's all you'll lose. But if you're serving as a reservist and you are in detention on the weekend, and you're serving at the armoury on a Wednesday night, why do you have to be a private on a Wednesday night? You're only supposed to be a private while you are in detention and lose that. In the case of a reservist, your loss of pay would continue for more than 14 days if you had 14 days' intermittent sentence.
Wouldn't that be the case? And wouldn't that be unfairly discriminating against someone in the reserves? Perhaps you can enlighten me on that. What's the confusion if I'm a sergeant when I'm in the armoury but a private when in detention?