Does Applying for Early Decision help/hurt Merit amount given?

Good Morning! My son is a rising HS senior and knows that he wants to go to St. Joes in Philadelphia. He exceeds all listed requirements for admission and should have no problem getting accepted so we are planning on applying for early decision this fall. My question is…does applying for ED negatively impact how much merit aid he gets because they know that he will definitely attend- therefore minimizing the need for them to try and pursuade him to register? Hopefully this question makes sense! New to process. Thanks!

Here is a recent thread on this exact issue:

http://talk.collegeconfidential.com/financial-aid-scholarships/2008678-is-ed-tied-to-merit-at-all.html#latest

Why apply ED if he knows he’ll get in without it? Sometimes kids change their minds over the course of senior year. Doesn’t St. Joe’s have a non-binding Early Action where he’d find out at the same time?