It looks like they are testing a satcom on the step platform:
View attachment 31690
IMO this gives even more credence to the likelihood that this platform is an intentional part of the final design and also that the amidships weather deck is unlikely to be at 02-level in the final design, otherwise this satcom would essentially be sitting flat on the deck itself. Also note that they are testing placement of the chaff/flare launchers on the weather deck at its current 01-level, further making an eventual 'raising' of this weather deck unlikely.
I think the placement of those possible chaff/flare launchers is the most convincing argument for why the platform deck may be the amidships weather deck so far.
That said, it's a little bit strange that they have additional chaff/flare launchers at the amidships position when the mock up had the port side ones atop the hangar structure instead... they could potentially be testing different positions on the starboard mock up, or it may even mean the real thing will have a whopping eight MRLS chaff/flare launchers...
However I wouldn't necessarily take the presence of a dome covered by a tarp as a convincing indicator of anything, after all they've added and removed a variety of antennae on the mock up over the last few years.
In the past they've had a green tarp covered antennae atop the white aft mast, as well as whip antennae atop the step platform, both of which have since been removed.
If the domes on the step platform that we see are a permanent or longer term fixture, then that could be more indicative... but by then we will probably have clear pictures of what the 055 actually looks like anyway.