I think the ‘key point’ missed is the $10 per 50GB once you go over the not-a-cap (in trial areas).
They’re trying to spin it that it’s not a cap, you can use as much as you’re willing to pay for - and that the 300GB ‘not-a-cap’ is a “plan” whereby you pre-pay for the first 300GB to give you the “benefit” of predictable bills.