Correct me if I'm wrong

So I finally watched this last night (I love The Conjuring Universe, but this one didn't look great...anyway). In the third act of The Conjuring 2, didn't Lorraine figured out by using it's name, she could send it back to hell?

So my question is, wouldn't Father Burke know this? He is literally one of the churches top exorcists/investigators and he discovers the name Valak at around the midway point of the movie and somehow doesn't know about this rule? I believe there are 20 something years between The Nun and The Conjuring 2, so they could say that rule was discovered in that time...but I'm pretty sure Lorraine didn't know that from a modern text.

Anyone?