You misunderstood the issue. If you don't have a [unapproved] screen protector on your phone, then the stored fingerprint can't be defeated by applying a screen protector.
That is a confusing sentence. If you use a third party screen protector then the fingerprint can be defeated.
I agree but I am curious how many iPhone owners enable this extra protection? For most people, it probably simply isn't worth the extra hassle.
It is enabled by default.