I think both are the same, Imeo made new Odysseus GGTS / Just GG bases, which is shorter on the GGTS connector side, so they sits flush on the Just GG collector tank.
Some older Odysseus GGTS bases didn't sit flush on the Just GG collector tank (there was a tiny gap left between the Just GG collector tank and Odysseus), so Imeo made new collector tanks for the ones that have Odysseus, and I think he is making now all the GGTS bases a little shorter on the connector side.
But maybe Imeo could clarify about this.