It is true that many of these little guns were sold which were chambered for the .44XL or .44-40 shot cartridge. It is equally true the actual .410 shotshell in 2" length was available in England & on the Continent during this same era.
I believe it is a mistake to assume the .410 was developed from the .44XL shotshell. By doing a search on the .410 several years back I found a very interesting site on the .410 which proved this beyond doubt with all being well documented.
I once had the pleasure of seeing a little German made .22 long/2" .410 combo gun which weighed as I recall about 3˝ lbs. This was some years back & I also seem to recall its proof marks predated 1912.
