CONGRATULATIONS! Yes, there was a group of students admitted in the first wave who did not receive a scholarship invite, and had a choice of April Explore dates - as far as I know, all of them have since received their Dean's letters and I am very glad to hear your daughter is among them!
I often agree with your last point - like you and your daughter, my daughter had no idea she would hear before April 1st. I was browsing College Confidential (I had not yet created a screen name) and saw on the USC forum that packages were arriving. I tried the "backdoor link" (which does not exist this year) and discovered that she had been admitted... walked out to the mailbox and found the package (which I locked back up in the mailbox and then I pretended I needed lamedaughter to grab the mail for me when she got home from school
Congrats again, and welcome to the Trojan Family!