I wouldn't necessarily say that scatter within one index means 2e although it certainly could. One of my dds had scores of 19, 17, and 8 on the PRI index of the WISC-IV a little over six years ago and really isn't a 2e kid (teen now).
For her, anxiety most likely played a huge role in that scatter b/c she was coming off a bad school year where she had been seriously stressed related to speed. She has always been more deep than fast. The test she bombed was the one timed test in that index and she flat out refused to complete it from what we were told.
My other one, who is 2e, has major scatter btwn indeces and some definite scatter within but not of the sort you're seeing or of the sort my older one had.
The information test is one that I'd see being fairly dependent on exposure b/c it is testing general knowledge. Similarities,OTOH, looks more at how words are similar. A child who reads a lot or who has lived in a fairly enriched environment might be expected to do very well on information. I'm not sure what a very low score on that subtest would indicate in the context of a gifted child. Hopefully someone else will.
