When you install
btrfs-tools, some hooks come with this to "install" btrfs support in your initramfs that come in boot to your system.
the files are
(you can check with
dpkg -L btrfs-tools) one alternative can be that after you install btrfs-tools, delete these files and after this rebuild your initramfs from /boot with
sudo update-initramfs -u
and with this your boot process will avoid to preload the btrfs module and try to detect any module on boot. You will need to do this any time that
btrfs-tools get installed/updated in your system. And you are going to need to do a
modprobe btrfs just in case, before plug-in your external disks formated with btrfs.