Not it's not. This doesn't look like an assumption to me but a hard date of end of support:
Hello, We have no regrets with our longtime support of FreeBSD, especially when others refused to do so. However, demand has virtually ceased and we do not feel justified in using development resources on a product that has reached a nearly 0% order rate. We're officially announcing...
forum.directadmin.com
Since you've been following the threads, I don't quite understand why you still call it an assumption?
I know you're experienced but do you really think that Plesk with Windows is better for hosting then DA (or Plesk or whatever) with a Linux distro?
However as for your installation, maybe
@bdacus01 will have some tips for you as he's also using FreeBSD.