I bought a 3060, thinking it should be enough, but also looked into step up if it weren't.  According to the official step-up faq, I should have to option to step up to a 3070, but it is not in my list of products.  Only 3070TI and up. Is there any reason for this?

If there is already a long queue of people stepping up to a 3070, then EVGA adjusts the mode off the road map until it is closer to being available. If there are (just a random number) 5,000 people waiting and they will never fulfill the 3070 step up before the next generation launches, then it becomes impossible to keep adding people to the line knowing they won’t get a 3070 because production will end, and they won’t move people over to the new generation that is released, because that wasn’t how the step up program was designed to work.