I think the context is why the info was posted. People were concerned (both in some media reports and certainly in hobbyist boards like NeoGaf) that at E3 (which was quite a while back), not all demos for XB1 games were running on final units. Some were confirmed to be actual final hardware, but not all. There was quite a reaction here. The same was true of the PS4, though the reaction threads didn't end up with the same sort of density of reactions.
Now, we're talking about public shows months later, and very close to the launch of the hardware, and the same scenario is still true of the PS4, while apparently not as much so with XB1 presentations. That's why the info was posted. Many people appear to have final, packaged XB1 systems in-hand now, but apparently the same isn't so for the PS4. We'd need more info to substantiate that last element.
Apparently the author of the Tweet thought it was meaningful to post. If you look at the concern by people here in that earlier thread about E3 at a much earlier point in the release cycle, all things being equal, it should make a lot more sense. Many of us though understand why you wouldn't use final hardware for convention-style presentations. This is much ado about nothing, but this is at least consistent with people's earlier concerns.