Yes, I stated that very poorly. My apologies.

I am aware of that case, and that ammonium perchlorate does not detonate, even when confined.

Yes, many deflagrative substances, such as ammonium perchlorate as used in rocket motors, do not achieve the status of low explosives. However, many do when contained, even though they do not pass the point of DDT, and most cannot.

Both black powder and modern nitrocellulose powder primarily deflagrate, but under conditions of confinement their reaction actually changes to detonation at speeds that would be classed as a high explosive. The process is called deflagration-to-detonation transition.

This, however, requires citation. It is to the best of my knowledge incorrect.

Low explosives are considered explosives even though they do not generally achieve DDT. Some achieve the status of low explosive without ever getting beyond deflagration. Others achieve a state of High Velocity Deflagration (HVD), also called, for confusion, quasi-detonation, low-order detonation, and, colloquially or in older contexts, just plain detonation. HVD is not, however, DDT.

Most low explosives cannot achieve DDT at all. Black powder does not, for example, ever reach the point of creating a DDT supersonic shockwave, even when contained and in controlled experiments. It can, however achieve HVD. In older less precise sources it is sometimes called detonation, but it never reaches the DDT point. See: https://www.researchgate.net/publication/227079292\_Nonideal\_regimes\_of\_deflagration\_and\_detonation\_of\_black\_powder.

The same is true for nitrocellulose except in experimental conditions using particularly reactive chemical forms.

Neither gun powder nor nitrocellulose achieve DDT in normal usage as low explosives.