It may not be an accurate summary, but GPLv3 makes extensive claims and none of that has been tested in court, so it is not unreasonable of them to be wary and

It may not be an accurate summary, but GPLv3 makes extensive claims and none of that has been tested in court, so it is not unreasonable of them to be wary and not take any risks. They abandoned plans to incorporate ZFS in macOS and implemented the inferior APFS instead simply because of a patent troll lawsuit by NetApp against Sun.