The abdomen and the digestive process go to Virgo, and the stomach itself is claimed by both Virgo and Cancer depending on which authority is being followed. That disagreement is not a discrepancy introduced here. It is in the sources, and tracing it shows how the scheme was actually transmitted.
The earliest full statement of the head to foot order in Latin is in Manilius, whose Astronomica was written in the first century, and his sequence is the one most later writers follow. But the scheme circulated for fifteen hundred years through commentary, translation, medical compendia, almanacs and finally print, and at every stage the boundaries between one sign's territory and the next were redrawn slightly, because the body does not have twelve natural divisions and the signs had to be fitted to it somehow.
The contested cases cluster where a boundary falls in soft territory or where a planetary rulership pulls against the positional order. The stomach sits between Cancer's chest and Virgo's abdomen. The kidneys are positionally Libra's and planetarily Venus's. The liver is positionally Sagittarius's and planetarily Jupiter's.
The atlas records the competing assignments where they exist and marks them as contested rather than silently picking the version a given source happens to give.