That was my understanding (to exclude Civil War vets).
Killed in action isn’t necessary to get into Arlington or the VFW. A Purple Heart got Stethem into Arlington, not his death by terrorists. Had he only been wounded by terrorists, he still would have had a Purple Heart and still would have been authorized for burial in Arlington upon his eventual death, years later.
A Purple Heart is also a qualification for admission to the VFW. See here: https://vfworg-cdn.azureedge.net/-/media/VFWSite/Files/Join/One-PageEligibilitySheet.pdf?la=en&v=1&d=20241021T210254Z
Purple Heart (not KIA) gets you into Arlington and the VFW. Also gets you free license plates in some states.