That’s interesting....Since .410 shotguns, are the only gauge of shotgun that is listed by actual caliber.(41 caliber)
It must be that the lands and the rifling are .410 and the free-bore is .45 caliber.
Modern shot sleeves will also form well to the irregularities of a rifled barrel I suppose.
For a good while, I owned a Derringer, double 6” barrell, either barrell could fire a .410 cartridge or a .45 colt. I used to keep a .410 in one and a .45 Colt in the other.
I am just wondering if they will carve out an exception for this and other similar revolvers.
My guess is "NO."