I did ask last night about this. The response was basically, the option to buy in full was there for about/around $70 a ticket or a way cheaper price than what went on sale. Not a great answer as it's not easy to lay out all that at once. I can't imagine them making that much on interest by making you get all 4 rounds at once.
I'm not sure why they couldn't do what is always been done which is you buy rounds 1 and 2 in full then go from there. If you don't buy rounds 1 and 2, you give up your seats for 3 and 4.
200 level is now about $2,200 per ticket for season tickets (basically $50 a game per ticket).