They don't have to *BUY* any coins. They already have them!
Why would would you as a builder go buy cheap plywood when you already have enough for the job? Sure, it's cheap plywood, but all the money you have to buy the cheap plywood is spoken for... to pay the construction guy's salaries for a while. What are you going to tell your contruction guys... sorry, I spent all your salaries on more cheap plywood?
I would argue from an accounting POV that these discounted coins are a liability against the declared value at retail. If Joe Blow paid $20 for the coin and uses it at a $20 value, its a wash. But if Miner Bob redeems his coin for $20 and it only cost him $7, he sees an increase in value of $13. That $13 has to come from somewhere and it comes out of GAW's pockets.
You know what is even worse for GAW? If more people spend their hashpoint converted coins than they project. Those coins are valued at $4 versus $7 from the mined coins. The only saving grace they have is that all the 'hashpower' people gave up to accumulate hashpoints gave GAW a healthy reserve to protect against a run. The fact that bitcoin has been poorly performing must have people sweating bullets. I am sure the don't want to eat into their fiat reserve from the outside investments... unless they took bitcoin instead.

To address your last comment, if GAW is not so liquid to have that scenario to occur, then they are playing with fire if it all goes sideways on them. They file for bankruptcy and then all of us who have some sort of investment with them are boned.