The Force was always on some mystical, spiritual vibe. There was no need to try and quantify who was open to it with a blood test. I feel the same way about Yoda; there was no need to show him flipping around and using a lightsaber.
Obi-Wan in ANH: "It's an energy field created by all living things. It surrounds us and penetrates us and binds the galaxy together."
Yoda in ROTJ: "Life creates it, makes it grow. Its energy surrounds us and binds us. Luminous beings are we, not this crude matter. You must feel the Force around you; here, between you, me, the tree, the rock, everywhere, yes. Even between the land and the ship."