If you don't trust Apple's FDE solution to not have a backdoor, you probably shouldn't use their operating system at all, as it has access to all of your data.
People usually aren't trying to protect their drive contents with encryption while the drive is mounted and the computer is running. If the drive is encrypted, anyone trying to gain access won't care if OSX has a backdoor because it will all be encrypted in the volume. The only thing that will matter is a backdoor allowing decryption of the volume.
You could use your argument to state that someone paranoid enough to use encryption just shouldn't use a computer at all.
