The number of times first and second names (or initials) are swapped around from one census to another almost outweighs the number of times they aren't.
I don't think that's anything to worry about.
I'd be more interested if a cemetery record could be found confirming the name of his 6 yr old son in Marshall Co, MS. I've seen trees that list him as David Addison Abernathy Jr ... but ...no cited source for evidence.
Then there is that WW I draft record of a grandson, clearly stating his middle name as Addison. Beyond that, I know no more.