+P is only a recognized standard for the following handgun cartridges:
9mm Luger (9mm Parabellum), .38 Special, .45 ACP, and .38 Super Auto.
You don't see much .380 ACP +P, because it doesn't technically exist. Major manufacturers usually will not load this cartridge over SAAMI standard. Virtually all .380 pistols are blowbacks, which makes it very important that the load adheres to nominal specs. Blowbacks are very load-sensitive, because the action will not necessarily remain closed long enough with overpressure ammunition.
Furthermore, you open an entire can of worms when you buy either +P+ ammunition of any type or +P in a cartridge with no recognized +P standard. Essentially, the ammo in question is advertising that it does not comply with industry standards. It could damage your pistol, or it could be a complete rip-off. Since there is no recognized standard, they can more or less load it however they want.
