Ava, I think the branch manager meant, if the concrete is raw or unpainted - then it is porous, once it is painted with any type of paint including an acrylic epoxy paint it is no longer porous. Therefore the type of sealer I would use would be different than if I had used a stain on the concrete - with a stain the concrete is stil porous but with an acrylic epoxy the concrete becomes non porous. Since that time I talked with the woman who originally put this treatment on her restaurant floor and she used an oil based varathane. However, I am going to use a water based or acrylic based varathane on mine. I have talked to several people and the water based sealer has less of a tendency to yellow than the oil based. Also I am thinking if I want to change the color or redo the concrete floor in the future, then I am thinking it will be less troublesome to redo a floor with a water based product. One point - I have tried using varathane with a roller before and it tends to put little bubbles in the finish, so I am going to use a flat sponge to apply the varathane. The woman doing the restaurant floor used a flat applicator to apply the varathane too. I am going to try my garage floor this week and will let you know how it turns out.

If the contractor said that the "stain is not penetrating the wood" and if that's true, then he's right, and you'd most likely just end up with more streaking if you tried to apply anything further. Perhaps the real question is why didn't it penetrate the wood? In any event, if it's not penetrating, you're probably gonna want to listen to the contractor if your really particular about that finish. It's possible that he could apply another finish over top of it that will have less ill effects but isn't willing to take that risk because he knows the 2nd application wouldn't be perfect either. If sanding is gonna cost too much, then maybe ask him or another to do another coat, even though it might not be perfect and tell him you're willing to take the risk. It entirely depends on what you find acceptable and what you're willing to live with. Ask him and gauge your odds.

staining would look more natural use a white stain

Yes, it will be paint and stain. We are planning to paint the rails and stain the deck surface.