Products that are shared between stores have slightly different descriptions on each store.
Exporting the product shows only the primary store description as it is supposed to.
If product is assigned to store "A" and the descriptions are ok but we need to bulk change descriptions in store "B" we are unable to do so via Export/Import unless we are missing something.
Suspect that the Additional Stores ("B", "C", etc.) have descriptions stored in DB but in fields not available in Export/Import.
Okay, I was trying to identify a way to do it without having to directly access the DB. I rarely recommend clients take that approach since the vast majority are somewhat novice when it comes to importing data directly into the db. That's why the import exists.
Suggest you post it as a bug in bugtracker if you are specifying the store on the line and it's being ignored.