That's a reasonable thing to exclude. But I'd argue we should just write the definition to caveat out of uniformed fighters fighting in war zones directly.

The reason is that stealth is necessary for planning a terrorist attack (and therefore redundant -- any violent attack on a civilian target is going to be stealthily planned almost by definition), and also not a pre-requisite in the after-math of a terrorist attack. In fact, most terrorist organizations brag about their attacks pretty openly. Even in some cases when they weren't actually responsible.