The Tosfos Yom Tov discusses some of you issues you raise and therefore gives his a different interpretation.

Short summary: Rabbi Elazar is only arguing about how much is necessary to be liable. According to R"E don't need any minimum measurement to be liable but according to R"M you need three lugin the amount he holds is necessary for nisuch hamayim on sukkos.

The Tosfos Yom Tov discusses some of you issues you raise and therefore gives a different interpretation.

Short summary: Rabbi Elazar is only arguing about the necessary amount of water to be liable. According to R"E one doesn't need any minimum measurement to be liable. However, according to R"M you need three lugin the amount he holds is necessary for nisuch hamayim on sukkos.