Historically, only the first class of the month - which has flows from Compass in it - get the drop before day 1. The reason for this, is because the Compass guys don't actually show up, so they have to distribute the drop via e-mail beforehand, so the OTS guys can get their training materials and sim training dates.

The second class of the month normally doesn't have flows, and is all OTS hires, so you will almost certainly get the drop on day one - 20 Apr in your case.

Good luck, and welcome to Delta!