Apparently Lubin's grades from a previous school are late in arriving. Therefore UConn's compliance cannot accept a LOI until the next signing period.
Hamilton didn't sign a LOI. He did sign a grant-in-aid. This is not binding. He did state he's committed to UConn. Apparently, he did this because of the difficulties his brother has had in the past. We'll have to hold our breath until late June when frosh arrive for summer school.