Raw (food grade) linseed will indeed harden off in the wood - as it oxidizes (dries out) it polymerises providing increased strength. The other good thing is that as it dries it doesn't shrink so it continues to fill the pores of the wood. So it is a really good wood finish.
However, the reason why I wasnt recommending it is because to does have a very short shelf life - just a few weeks even if refrigerated. Fresh, linseed is a thin oil and penetrates easily. However, if it's already oxidising (going rancid), then the polymerisation is happening before you apply it so, even if it does not seem much thicker, the molecular size is much larger and it won't penetrate anywhere near as well. So the oil will sit more on the surface plus it will smell and taste unpleasant.
So, if you are prepared to go and buy fresh linseed oil as you need it, then it is great but if you're going to have a bottle stuck in the workshop for months on end, then I wouldn't use it - that was my reservation given that that is exactly what most people tend to do.
Olive oil is a much more viscous oil - if you apply it without heating, it will give a nice finish but won't penetrate very far- so heating is a good idea to yield a long lasting, food safe treatment that won't smell or taste rancid. It won't polymerize though so it won't strengthen the work piece if that is what you are after.