The plastic shine in tru oil is from the natural oils that have had driers added to the finish to make them hard, and sit on top of the wood.
Set a glass of water on a tru oil stock, and you'll have a permanent white ring. The linseed in it never dries.
Tru oil was and still is the standard for fun stocks for years and years. There are many others out there as well, Linspeed, Pilkinton, etc. they all use the same artificial driers to achieve that shine. To mellow out that shine, you must use pumice and rotten stone to get that "hand rubbed" finish. OR you can just hand rub a nice finish that becomes part of the wood.
Don't mean to ruffle feathers, but this is the truth. Linseed oil is NOT a finish, it's an oil. Gotta add driers and hardeners to make it work.
A spar varnish in my opinion, would make a better outdoor finish. After all, it's meant to be used on boats.
JMHO!