I do find things here a little perplexing because of the strange methods and the strange use of products.
Red oil in the English method of finishing is a colouring medium applied in several coats to give that desired red colour to the wood. It is not a finish in its self.
I do not understand why people use a mild abrasive powder i.e. Rottenstone as a grain filler there are far better things to use, it is normally used to finish the final coat to give a deep lustre rather than a mirror shine. Rottenstone being an abrasive by using it to fill the wood pores it soon dulls the edge on chequering tools.
Finishing oil is applied after grain filling, this oil has a siccative some form of resin to produce a hard but flexible surface that brings some protection from corrosive hand sweat and of course water, but not to the point that it is totally impervious.
The reason a finish that is totally impervious to water and water vapour is that it acts like a box, what ever water can get in is kept in.
I am sure you have all seen timber when varnished no matter how good the varnish water and moisture always finds a way of getting into the wood underneath the varnish. Wood is a natural product that breathes and moves with the seasons so a thin flexible finish that allows the wood to move is far more favourable than a hard unyielding Epoxy finish that will crack over time.
The English waterproofing of fine gunstocks is wax polish applied sparingly and often.
This method of stock finishing gives a warm natural waterproof sheen as in the photograph.