If I remember right, Spock goes back in time because he realizes something is off. So, could Data being in command of the Enterprise be the first thing that Spock realizes is off?
I haven't heard anything about that being the reason Spock goes back in time. Besides, if the timeline had changed around him, how would he know? He's not Guinan.
Don't you remember The Mark of Gideon? I don't know how long it takes Kirk to figure out he's on a fake Enterprise but Spock figures it out in like 3 seconds. He may not be Guinan but he's Spock, that's how he knows.