I think the preschool skills are really hard to quantify and depend on the child. The levels really have more to do with how quickly a child masters something after being introduced to it. There's an item in the level 3 list that says

"Most spontaneously read with or w/o previous instruction before kindergarten"

Well, what defines instruction? If you are reading to your child for an hour or two a day, isn't that instruction? Or you play phonics games and teach your child the ABC's, isn't that instruction? And how does the child that gets 30 minutes of reading a day compare to the child getting hours? But on the other hand, if your child is raised in a home speaking and reading English, they aren't one day just going to break out and read Spanish regardless of GT level if there is no exposure.

Before kindergarten, my DS maybe would have been labelled a level 1 or 2 based on the Ruf lists as they are. But would now in first grade be labelled level 3 or 4. We did not "hot house" at all. We mostly read at bedtime, but let him explore on his own. But if the Ruf levels had items on visual spatial things like following directions to construct lego sets for 12+ year olds - hey, we'd be level 5! Or ability to grasp and explain conceptual math. Or maybe the ability to ask too many complex questions in less than 24 hours. He could not read at the start of kindergarten, to my knowledge, but I don't ever remember handing him an early reader and him struggling with it. He reads very long and complex chapter books now independantly, that my 5th grade niece wouldn't approach. So, even though we never observed him reading before kindergarten, he clearly has it in him to be an advanced reader.

So I do think the content of the lists is somewhat subjective and perhaps just a guideline that may or may not be accurate for your child! YMMV!