Based on a quick survey of where these companies were recruited, most appear to be from Talladega and Randolph, which shared a common boundary. It's quite possible that a man might have been discharged from the 25th Alabama for injury or disease and reinlisted in the 7th Cavalry and served for a time with that unit. Due to advanced age or disability, he might then have been reassigned to Hardie's Reserve Cavalry. Just speculation, you understand.

The only stray in the list is Company "B", Livingston's 8th Alabama Cavalry, which was recruited in west central Alabama, and it's still worth checking.

I have access to the service records and may be able to help if needed.