Imagine torturing someone with only "moderate" pain. I can't imagine anyone "breaking" for a stubbed toe. If part of the interrogation is moderate pain that goes on indefinitely, then someone might suffer enough to "talk," but I think at that point we're talking about mental suffering. After all, water torture causes no physical pain, but it's still torture. In short, if the interrogation isn't severe, it won't work on anyone.
Our would-be torturers are left with a choice:
- "Moderate" interrogation techniques that don't work.
- "Severe" interrogation techniques that are illegal.
Asking "is it really torture?" sounds to me like asking the cop "what's the worst I can do without being arrested for assault?" Wanting to know where the line is implies wanting to cross it but willingness only to get close to it.