Both movies have adopted a neo-noir skeleton involving hit-men, a category that gives rise to more than 100 neo-noirs. I consider the two films together to help me decide, and I decide that both are philosophical neo-noir. Once the clothes are placed on the skeleton, it's still there and it's undeniably neo-noir. A similar observation of the skeleton might help me to consider Lost Highway and Mulholland Drive as neo-noirs, rather than to doubt them. In these two cases, the skeleton is the workings of a person's mind, and neo-noirs that use that to hang the story's clothes on are frequent. Often this is referred to as involving identity.
Hit-men and identity (or fragmented thinking), what else is quintessential neo-noir? Schemes involving money, sex, insurance. Many such stories floating around. What else? Surveillance may make a small subset. More prominent are stories of criminality of upper echelon pillars of society. Backwoods or rural crime has gained a lot of ground. Revenge is a staple. Pathologies. Detectives. Serial killers. Attacks on the defenseless.
These things do not define neo-noir, but they may help to identify its presence. I'm not using a noir-meter here. I think that you look at a movie and you often know what sort of movie it is within a fairly short time, like 15 minutes or less. The presentation tells you by a variety of cues.