Here's the other thing: those RSUs may still be restricted. According to the article, Juno launched "right around this time last year". Those RSUs may not have vesting schedules <12 months. Which could imply the company is, in fact, accelerating vesting at a % of the total value. Combine a <100% acceleration with some liquidation preference math for preferred stock, and there you go.

This is all conjecture. We have no idea how many shares are outstanding, liquidation preferences, etc. We don't know if RSU-holders are being "screwed", or how. The suggestion that the "par" price of a RSU is $0.20 could be "what-if" math. ("You could take $100 today, or 500 RSUs that might be worth even more in the future!")