I think if you draw the basement on flat ground -- not the ground floor of the house -- you can recreate how basements were before the terrain editing update. Then you do get the awkward transition when the stairs go through the foundation, but it does keep the ceiling of the basement at ground level, as opposed to top-of-foundation level. It's worth knowing that.
I discovered this when building the Reasonably Priced Mansion on Vacuous Green on the building thread. On a big lot like that, it's fine to keep the basement size to within the size of the house above. I worked around it, caused some design issues, had to move the money vault to where it is etc. But on a tiny 20x15 lot where max space is wanted I'll take the awkward stairs through the foundation. Like I said, in that case, just draw the basement on the terrain, not the house.
Disregard if this has changed!