I believe they got behind on their hiring quota early on and have gone through the 300 with training seats still to fill. I asked about the process during the interview and was told the initial hire rate was 40% in April. Was told at the time of interview last month the hiring rate of those interviewed was 78%. A little public math shows why they might be contacting those who did not get a Mar 4th email. 5 months of training classes at 12 seats per class per week, 48 per month. 300 emails means that they needed to hire 48 out of 60 interviewed each month. Just my 2 cents of course.