These definitions are manufactured by HR. Being fired means being fired. What reasons the company had for it are irrelevant. Most employment in the US is at will, so the company doesn't need to provide a reason for the firing. In fact they don't even need to have a reason.

Plus most layoffs are also taking performance into account. If every department is tasked with cutting headcount by 10%, they aren't going to pull the numbers out of a hat. The lowest performers will be the ones shown the door.