The 'experts' say that there really is no such thing as a 'warped' rotor. The pulsation that people feel isn't a result of a rotor that is warped, but since the feeling presents itself that way, that's what people will say is the issue. The issue is actually deposits (brake material) that end up, in a sense, 'welding' themselves to the rotor and then cause an uneven surface for the brake pad to press against. And I'm no expert on the subject, just sharing what I've heard and read.
And I agree with you on your other point. For the first 600 or 1000 miles, it does make sense to err on the side of caution and be 'gentle' to your new engine....no over-the-top revs, don't idle for extended periods, and don't get on the highway and put the cruise control on 70 and keep it there for 500 miles.