Is that true with 4.10's or is it more applicable to the stock 3.27's? I personally never noticed where the RPMs drop to when I shift from 1st to second, I'm usually concentrating on the road ahead of me and just being mindful of the RPMs in corner of my eye. That's one of the reasons I got a Raptor shift light. When you are on the autocross grid or road course its a bit more difficult to make sure you are shifting at exactly the optimal RPM since you are trying to coordinate an process so much. I'm sure it gets easier with seat time, but for my experience level it is still a demanding task.
It's still true with 4.10s. The high rpm shift is most critical on the 1-2 shift because of the 3.37 to 1.99 gear drop, that creates a big RPM drop. The 1-2 needs a good 6800-6900 rpm shift.
The 2-3 and especially the 3-4 don't need to be quite as high because the gear spacing is closer. You still need to shift well past peak power though.