It is an experimental feature on FreeBSD 14-CURRENT. It will be merged into OpenZFS eventually (and maybe backported to FreeBSD 13-STABLE and whatever new point releases happen).
Where do you see it in CURRENT? AFAICT FreeBSD main is still more or less just a sync against OpenZFS.
AFAIK it's being developed against FBSD, but is not any more integrated there than it is in the main OpenZFS project.
Fair point, I haven't actually looked at CURRENT, it's an assumption from the "goes live" part of the article :)