Makes sense you would have only heard of real-time, I think the Van Buren Tech Demo only has real-time working.
To know about turn-based we would have to dig out Van Buren's related material, like old interviews and forum posts. Here are a few quotes that can be found here on NMA:
This next quote is also from NMA but we have to access it using the
Internet Archive:
Hopefully, these next quotes will link to the thread where these are found, in case anyone wants to read it, although it's a short thread with only around "one and a half" pages of posts: