Unless they were lying together in the same field hospital, I don't see exactly how these records could have gotten crossed up. Clerks were working with original registers of hospitals &c. and made cards for each name found. Cards then went into service file packets. Cards and documents are sometimes misfiled, which is easy to spot (if you look carefully) on individual cards. Unless documents were original to the 1861-65 period, the War Department would NOT accept papers from individual states.