Notify value of variable that holds a nested fact - Puppet4

I am trying to understand what the difference is between the following:

$major_release = $::facts['os']['release']['major']
$selinux_is_enabled = $::facts['os']['selinux']['enabled']

If I put in my manifest:

notify { "major release is: ${major_release}": }

And then run this on my client side, it returns a value as expected. If I do the same for the selinux_is_enabled variable, it does not return a value, even though a

facter os.selinux.enabled

on the client side returns a "false".

Can anyone explain why the notify does not return an expected value for selinux enabled but it does for os release major?