The exact same error in one of my family manuscripts placed my GG Grand Dad in the 2nd Mississippi Infantry Regiment (of Gettysburg Fame)

Although it was initially exciting to read this "revelation" in the manuscript, the facts didn't add up. #1. That regiment was from Northeast Mississippi & he was from Marion County
in South Mississippi. # 2. As a forty-something year old man in 1861, I doubt that he would have been eager to join the kids up around the Tennessee state line in their
race to be among the first Mississippians to Virginia. #3. I'd never heard any family stories of an ancestor that had fought at Gettysburg.
After more research, I discovered that he served in the 2nd regiment Mississippi State troops, a militia organization from south Mississippi. ( Still an interesting story )
... but far removed from the 2nd Mississippi Volunteer Inf. Regiment.

I never thought this was intentional. As Alan said, many genealogists see names on roster ( and in this case numbered regiments) and jump to conclusions.