I work with collagen glues and boiled linseed oil all the time, and they work great together. I have made wafer thin all-natural composite materials using wood fibers (thin plane shavings) as the substrate, hide glue to hold it together and thoroughly impregnated with boiled linseed oil with a beeswax top coat. The result is a rather strong material that's lightweight and thin enough to let light through.
It is plausible that they would have used boiled linseed oil instead of or in combination with hide glue or other materials commonly used in that era (bitumen, beeswax, etc).
I call it "basket weave veneer", made by taking thin plane shavings, boiling them in a kettle and straightening them under weight and finally weaving them like a basket and applying some glue.
Using (liquid) hide glue is essential in this job. With a PVA glue, you'd end up with a blob of plastic. Unlike PVAs, hide glue doesn't interfere with the finish (BLO).
I did a few prototype sheets with the intent of making a lamp or lantern but never completed the project.
It is plausible that they would have used boiled linseed oil instead of or in combination with hide glue or other materials commonly used in that era (bitumen, beeswax, etc).