Look in the SF Bay area we have very many multi-million dollar homes that are built into hillsides where only the garage is above grade facing the road. You step down to the main entrance and below that you have 3-4 split levels. You have stairs going up each side. Maybe a small elevator taking you to the garage. Each living area is built out from a foundation that puts each living area above grade of the hillside to the left and right. It is mostly on bedrock. Yet ANSI Z65 says the entire level must be above grade. "Level" isn't defined of course. Stupid ANSI. We assume from the context of the entire standard, that they do mean that the entire level including the foundation and retainer walls must be above grade
Using common sense, however, such hillside homes can be far more advantageous than living in a completely above-grade house that is however in an area of liquefaction - such as much of Foster City. ANSI fails to understand these things. It was really molded by builders, with little input for appraisers. The people involved in writing ANSI, are really not very competent or experienced. I would assume most are from the East Coast.
Anyway, it is what it is.