Seeing just how large that central ring is in situ, and knowing that it's apparently as tall as a 6-story(!) building, I have to wonder if perhaps the off-center location might have been a result of the American Adventure laser that creates images on Spaceship Earth, which runs directly along the park's central axis.
As a quick comparison of scale, here's what the Earth Barge and new structure look like when passing through the drawbridge (different angles and zoom, obviously)
ROE's Earth Barge was a 28' diameter globe on a 10' pedestal, for about 38' total height; the solid sphere used in the earlier Illuminations productions was slightly smaller. The American Adventure laser appears to be approximately 40-45' above ground level, which in turn is about 10-15' above lagoon level in front of the building. This would provide adequate clearance for a laser to pass over the barge and continue on to SSE beyond. However, with a new structure that's 60+ feet tall, perhaps it would need to be offset from that central axis to allow the light to pass.
Without seeing it in person, it's tough to judge exactly how far the spread of the laser would extend, but it seems plausible that the ring could get in the way, blocking the lower portions of SSE, and that having it off-center was a deliberate decision.
However, Occam's Razor states that the simplest explanation is usually the right one, and knowing WDI's recent efforts, they probably didn't even consider moving the mooring, regardless of any impacts to the existing lasers. When the show eventually opens, I don't doubt that the new structure will be hit with stray lasers simply due to its colossal size and desire for an over-the-top show; the more restrained iterations of the past never seemed to have this issue.
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