Both my kids went to schools where merit was awarded for certain scores and GPA. One school was quite clear that if you had X gpa and Y score, your merit aid would be $Z. There were also other awards you could earn. The other school was a little fuzzier about the amount for the score/gpa/class rank numbers, but you could get a pretty good guess by the prior year’s awards. They also had other merit based awards for EagleScout/GS Gold awards, robotics, siblings, etc.
Neither school had ED but both had rolling admissions. They were admitted LONG before FA/merit notifications came out, but of course different from ED because they were free to choose other schools.
IMO, schools should give the same merit to an ED candidate as to RDs. The student is signaling that this is their favorite school. A school is being unfair if they want the student to commit ED but then only give merit as bribe money. Do they want the students who want them, who want to be there?