OK Kitbag I'll bite. The official designation of the wing shape for the F35 is the so called large area clipped delta. Very similar in shape and design to the F22 wing, but on a smaller scale. I agree that it is not a purists swept wing, but for the layman the leading edge surely satisfies the criteria of a 'swept' wing. To compare it to the F104 wing is, in my opinion folly. Two very different design drivers at work.
Any and all aircraft will have a small RCS from 'certain angles' the key is knowing where those angles are.