Nope. If you return it after 4, you can leave it with the Valet (along with the keys, to avoid additional charges). If you return before 4, you probably should go to the rental counter inside.
And instead of walking to Epcot, where you'd have to enter and walk all the way through the park to get to the buses, walk or take the Friendship boat to Disney Hollywood Studios, where you can board a bus back to POFQ with much less effort and no park entry.
eta: But why NOT return to the Car Care Center? Ask for directions at Bell Services (there's a shortcut if you turn right out of the access road) and at least the CCC will drive you back to the resort's front door. Seems easier to me, even if Bell Services doesn't know what I'm talking about.