Very good question! I believe they are simultaneous positions. Skyfield has facilities to calculate the light propagation adjusted position but i didn’t use them. Would you have? Is one more “correct” or more likely to be anticipated by future sentients? I’m always unsure about ther design details.
Also there is an other skewiness. Because obviously the drawing is not to scale the moon position can be correct from the sun’s coordinate frame or the Earth’s coordinate frame, but not from both. I choose to make the moons “correct” in the sun’s coordinate frame. Meaning that if you were hovering over the ecliptic frame looking down at the Jupiter during the wedding and rotating the pendants so the sun is in the direction the real sun is, then you would see the moons under you in the same arangement as they are on the pendant. But if you would stand on the surface of earth (during the wedding) and look at Jupiter you would see the moons in a different arangements than a tiny human standing on the earth dot looking at the jupiter dot. (And not just because of the time delay difference, but because the coordinate systems are different.)
Which is weird. Because the wedding happened on Earth, not hovering over the plane of the eliptic over Jupiter. So maybe that was a weird choice. (And not even talking about how north-centric it is that i decided to draw the diagram from the “north” looking down at the eliptic, instead of from the “south” side. These are all kinda culturally driven arbitrary choices. Would love to have none of those present but I haven’t found a good and principeled way yet.)