I'm not Cathy, but I'll jump in! Like you, I always remember reading, but I don't think I was three, probably more like 4. Definately before K. K wasn't my year! DD8 taught herself around 4. She definately started with phonics and I would guess whole word reading came a little later.
DD5 seemed to sight read at three, but it never developed into anything. I showed her how to sound the word out, she demonstrated that she could a little, but never really was interested in doing it.
Flash forward to now, she has been whole word reading only. She asks what a word is then it's memorized. She was reading by memorization only. She definately knew what she was reading, just did not attempt to sound anything out. And she is not spelling like DD8 was at this age and I wonder if it's because she doesn't understand phonics. I mentioned before the girls go to Score and they suggested that DD5 use Headsprout and told me she would learn phonics. I did feel it was important for her to understand how it(phonics) works. After 4 or 5 times on the program, she just starts sounding out words, it just clicked. They want her to move out of it, but I want her to finish just to solidify it for her.
Consequently, I'm not sure in the GT crowd the early reading factor can necessarily translate into levels of intellligence.
I've just been told by the psyd. that specialized in GT kids that he know believes that C-dog is more intelligent than older sis. He's supposed to be the best guy around here, so I won't second guess it. However, if he is right and she was screwing around the first time, I may have him attempt to re-test with the WISC or SB. Currently the school is using C-dog's lower score as a reason they can't accomodate her to the extent they accomodate big sis.
So yes, I think I can say with some certainty that younger sib can definately be a hider. Although, perhaps they are just intelligent in different ways.