Good morning . Linseed by itself isn’t a very good sealer . Only about 10% impervious to moisture . Because of this , you can stain through linseed .
Tung by itself is to good of a sealer ,. Close to 90% impervious to moisture . Because of this , its very hard to get a stain through Tung oil
So by placing a couple light coats of tung over your linseed , you get the sealing properties of the Tung oil but the ability to repair if you ever need to as the linseed holds the tung from penetrating the wood . But at the same times , the Tung bonds very tightly to the linseed . So it will not flake or peel
The tung will also provide you with a shine that can be dulled back if you like.
I cant say that Tung oil will prevent fading . You will notice the figure pop even more then what you have now . It will also define it more .
But with all of that , it also has a tendency to darken a bit