thats a good question but you have to remember the time it was made. before 1914 there were no real industry standards for cartridges and chamber dimension. there was a first attempt to normalize some catridges and the 10,75x68 was imho one of them but it was an early start and not a law everyone had to watch.
the free bore was not seen as important in the old times. here is a chamber cast of 20/40 rifle barrel taken from a combination gun by Funk in Suhl.

this gun have damascus barrels and is Blackpowder Only it was probably made in the 1890s. you see that there is also no free bore just a short cone to come from the chamber ( the black line show the case mouth) down to rifling. this gun was made for thick wall paper shells.
with blackpowder loads pressure spikes are not the problem but I think there was trial and error over a long time before the free bore was seen as important for holding the pressure down. your rifle could be absolut safe without a free bore but I would feel more comfortabel shooting it with a correct chamber.
to answer your question I have made chamber cast's with paraffin

you see the chamber of 10,75x68 made in 1950 in france, a RWS 10,75x68, a 10,75x57 handload and a chamber cast from a 1930s Gustav Genschow M 98

the pen shows the beginning of the rifling it starts low and become deeper than so it was a real cone