True, but Linux is also a first-class citizen in the OpenZFS project. The argument that was made earlier is that FreeBSD is so nice, because of its superior ZFS integration. This has been true for a long time and as such I agree with OP.

However, since the ZFS code basis is now the same for Linux and FreeBSD (which I also agree is a good thing) I don't think we will have the same superior FreeBSD ZFS argument anymore. And people who are in favor of FreeBSD over Linux have to provide other pro arguments than ZFS in order to make a case for FreeBSD.