Belle, I finally saw your PM to me this morning and sent you a reply, though I was concerned that it was too late.
One more thing - I'm generally a big fan of getting people to show me where exactly the rules say that something can or cannot happen. More times that I care to count, what they tell you the rule or policy says is not really what it says and you can't know that until you see it in writing. Usually, if it's not in writing, it's not really true. I'd be asking them to show me where it says that homeschoolers can't use the gifted services and then I'd probably be having a casual conversation with the state Dept of Education to find out why. I don't know much about the homeschooling rules, but I've heard homeschoolers can participate in extracurriculars like sports, why not academics?
Unfortunately, that still means you have to decide exactly how far to push the issue if they give you a hard time (whether you want to resort to some sort of due process or legal action) in order to get them to follow their own rules. Since you are homeschooling you may not be as concerned about the fallout that may come from challenging the powers that be, but you also have to balance how much time you spend on an issue that you can solve on your own.