Well, I did put a disclaimer by using the standard terminology :) Fiction is good for suggesting possibilities, you cannot derive evidence from it of course.

I agree on the first-minute point, but do not see why it's relevant, because there is the 999999th minute by which value drift will take over (if altruism is strongly related to empathy). I guess upon waking up I'd make value preservation my first order of business, but since an upload is still evolution's spaghetti code it might be a race against time.

Perhaps the idea is that the sensory experience of no longer falling into the category of "human" would cause the brain to behave in unexpected ways?

I don't find that especially likely, mind, although I suppose long-term there might arise a self-serving "em supremacy" meme.

their environment would not cause this to change unless the same sensory experiences would have caused their previous self to change.

I don't see why this is necessarily true, unless you treat "altruism toward humanity" as a terminal goal.

When I was a very young child, I greatly valued my brightly colored alphabet blocks; but today, I pretty much ignore them. My mind had developed to the point where I can fully visualize all the interesting permutations of the blocks in my head, should I need to do so for some reason.