Stain or dye needs to penetrate in order to work. The idea of sealing the wood is to prevent moisture from being introduces to the wood. Can't stain/dye it if it can't get into the pores.
I don't know that you'd NEED the sealer coat of shellac with tru-oil. Every barrier finish (which tru-oil is) seals the wood just fine with the first coat or two. The subsequent coats build up the thickness. So, for pure sealing purposes, the shellac would be un-necessary.
Now, you've introduced color to the wood. With that, you'd need to consider if the solvent would draw the pigment from the wood, dorking up the whole process. To the best of my knowledge, grain filler doesn't become solvent again after it dries, so whatever solvent is in the finish would not draw the pigment out. If you do stain/dye the body, repeat the whole process on a piece of scrap and test everything on there. Alcohol, shellac's solvent, might draw the pigment, as could whatever is in tru-oil.