I don’t know that this is 100% true. You would have to be sure that never happens for any student at any college.
With the opacity of admissions at this point, I don’t think we will ever know exactly why they each do what they do. Some of the colleges that have added merit in April do not seem to be hurting for applicants. Perhaps the merit had nothing to do with whether someone has or has not accepted but is simply the timeline of the merit process at that school.
But it is also possible that, like those who will listen to a need appeal from one student but not another, they may really want that one student but not another. To know one would have to find other comparable students and figure out if they also got some extra merit.
I think this thread is useful whether or not the merit is actually a bid to get someone to come or just a last minute addition as scheduled because in either case the premise stands: if you are interested in a school, but finances are a problem, maybe don’t give up until the last minute.
For instance, my S is the Baylor applicant who has had two additional rounds of merit added in the last ten days for a total of $10,000 more a year on top of generous merit awarded at acceptance. We don’t know how each of those awards came about, i.e. did someone ahead of him turn down the competitive weekend award so he moved up after being told in March that he did not win anything from that? Were the awards in another category always scheduled to be released on April 19? Who knows. What we do know is that if he had already declined two weeks ago over the cost, we would never have found out that it is now $10,000 less a year. (These are all merit, not need-based adjustments.) Baylor has no trouble filling its class. They had 33,000 applicants for about 3400 spots, so that is not the reason.
Our experience this year has been that waiting has worked out well! Some scholarships trickle in. Who knows for what reasons?