Yes, but it does not smell like human decomposition. The smells are very very distinct and different. There is more to a large mammal than meat, (fluids, bowels, assorted organs etc. Meat is really just muscle) and it all contributes to the overall smell.
Now maybe if there was a reasonably large dead mammal in that trunk for the better part of a month, say a largish dog or a pig, then yeah you might be able to get something that might possibly approximate that smell to a human nose. But the dogs still would not have hit on it. A squirrel would not have smelled the same to someone who had encountered the smell before (George with 100% certainty). Pizza or rotting meat absolutely would not have been close.
Now to further this. We are still animals on some levels. We do have some hard wired instincts remaining. One of the big ones is hard wired into that smell and only that smell. You can smell rotting meat, garbage, pizza, even a dead squirrel, and it will be awful. It will be horrible. You will want to throw up. You will think on reflect on how horrible the smell is. But you will not react the same as you will to the smell of a human decomposition event. As soon as you smell a dead body things happen that don't happen typically with other odors. Adrenaline kicks in, big time. While the garbage and the squirrel may make you think "Oh this is awful!" and "I'm going to be sick" that smell of a dead person triggers on an emotional level the single inescapable thought of "DANGER!!!". It isn't mysticism or speculation. Like all other animals we react to the smell of one of our own that is dead.
Cindy's growing unease about the car while she was at work was largely because of those instincts that kicked in when she encountered that odor. The fact that her manager sent her home is a reflection of how obvious her distress was to an outside observer, regardless of what she specifically said.
