Are they cooking the books on combat deaths?

Including only the combat deaths of US troops (not soldiers from other countries or civilians), these are the figures for three of the last major wars:

Vietnam             1965-1975                  58,226
Iraq                    2003-present                4,459
Afghanistan       2001-present                3,229

These figures are tentative but somewhere in the ballpark of current quoted combat deaths. When I once visited the Vietnam Monument in Washington, DC, the park ranger  had a thick telephone book with alphabetized names of those who died since the monument lists them in order of death. I was told by the ranger that only those who were injured & died in Vietnam were listed on the monument; if you were injured in Cambodia or Vietnam & died on a ship on the way to a hospital in Japan, or in that hospital in Japan, or in the US as a result of injuries incurred in the war, you are not listed on the monument.

Given the huge disparity in the reported combat deaths between these three wars (all of roughly the same duration), does anyone think the Pentagon is cooking the books on casualties? At least in a more malignant way than they do with the Vietnam Monument?