The "android body" is not just an empty receptacle. As I've said repeatedly, it has fundamental differences from Data's original body and brain. Physically, it has a lot of abilities Data didn't have, and neurologically, the firmware and operating system of its positronic brain are significantly different from those of the original Data's brain. Basically this is the Soong android's brain, a brain designed to replicate the living Soong's neural architecture and personality, but with Soong's memories wiped and Data's loaded into it.
What you're assuming is that Data's memories represent the entirety of what Data was, and the book does, in fact, make clear statements that conflict with that assumption. It establishes in Soong's internal monologue that there are two components to consider here, Data's memories and his programming. The reason downloading Lal's memories into Data didn't turn Data into Lal, and ditto for Data and B-4, is because they were just the memories, not the operating system itself. Soong's intent was to create a new body for Data with an operating system that could handle Data's, err, data, since B-4's OS couldn't handle that load without crashing. But that new body was destroyed by the Borg, and ultimately Soong sacrificed himself to let Data have his body -- and that comes with the distinct hardware and operating system of his brain, which were designed for Soong rather than for Data.
So while this new entity has all of Data's memories, he still has Soong's brain structure, which could mean he'll retain aspects of Soong's psychology or personality. Or that the parts of the two beings could synergize in unpredictable ways.
And again, my point is NOT that anyone has to believe it really isn't Data or that it really is. My point is that it doesn't matter. Those who want to believe it's the same being are perfectly able to do so if that's what satisfies them. But those who want to believe it isn't are equally justified to come to that conclusion. There's no point arguing over it because it satisfies both groups.
But whether you think it's the same Data or not, he's still changed. It's not just a return to the status quo. He won't just be back at the ops station on the Enterprise giving exposition. He's got a new outlook on life, a new set of goals. He's turned down the offer to return to Starfleet and gone off on a new quest of his own, seeking the Commonwealth of AIs. He can even use contractions freely now. As I've been saying, if you're going to resurrect a character, that's the right way to do it -- by making it a new direction for the character rather than just a lazy reset.
I've got a sneaking suspicion that I'm going to be left in an uncomfortable place regarding it; I'll explain more, naturally, when I've finished the book and discovered if I'm right or not.
